Diame powers past Wilshere after showing nice feet and plays it out wide to Taylor, but when the ball comes back to him, his touch is heavy and he catches Mertesacker on the ankle as he clears. That's no way to treat a future team-mate now, Mo.
The officials have revealed that there will be 12 minutes of stoppage time now as Arsenal continue to bang their head against the West Ham back four in search of another goal.
CHANCE! Walcott goes close twice in quick succession, firstly with a lobbed effort that Jaaskelainen just about gets back in time to collect and then with a glancing header after an Oxlade-Chamberlain cross.
Some good news to bring you folks, reports are filtering in that Dan Potts has regained consciousness finally.
Credit to Arsenal here as they continue to attack, with Oxalde-Chamberlain the latest to try his luck from distance only to se Tomkins get in a good block.
CHANCE! Corner after corner keep coming in and West Ham look dead on their feet here begging for the final whsitle as Cazorla sees a drive flash wide of goal.
The 100th minute has just ticked over now and we have two minutes left to play as Andre Santos screws an effort just wide of the bottom corner.
89'
Cazorla whips in a corner and Mertesacker gets above Reid at the near post, but the header lacks power and is hoofed away.
88'
Ramsey runs down a blind alley and has to turn back on himself and look for Wilshere inside, with O'Brien getting back well, but Arsenal still look menacing here.
86'
Substitute Oxlade-Chamberlain attacks O'Brien down the right, with Walcott shifted into a central role now after Giroud has gone off, but his cross is disappointing and the goalkeeper plucks it out of the air.
85'
CHANCE! Wilshere is given far too much room on the edge of the box and his low drilled effort is spilled by Jaaskelainen only for Demel to collect and run the ball out of play.
84'
Understandably the game is lacking a bit of tempo now but Arsenal are still dangerous as they flood forward looking for a sixth.
83'
The game resumes and West Ham are still losing 5-1, just in case you'd forgotten the score.
82'
Potts gets a lovely round of applause from the cheering homes fans as he's carried off the pitch so we'll likely be having quite a bit of added on time now.
79'
It initially only looked like a minor collision to Potts, this, but it's been a full eight minutes now. The young left-back is now getting oxygen and having his neck put in a brace on the stretcher.
77'
The camera cuts while Potts is receiving treatment to West Ham manager Sam Allardyce, who is scowling like no man has ever scowled before. He won't have been at all pelased with his team's diabolical defensive display this half.
Minute
Description
75'
Potts is still down and surrounded by medical staff as they try to get him onto a stretcher. Few worried faces out there now.
73'
A. Oxlade-Chamberlain enters the game and replaces O. Giroud.
Potts is down in a heap and in need of treatment on the pitch for what looks like a back strain and Giroud is subbed off by Wenger for Oxlade-Chamberlain during this tiny break. Why on earth has the Frenchman been taken off there when he's on a hat-trick. Pointless.
71'
Blink and you might have missed it among all the action this half, but reported Arsenal transfer target Mohamed Diame has just come on for West Ham. Could this evening get any better for Arsene Wenger? He even has the chance to do a spot of scouting now too.
70'
M. Diamé enters the game and replaces Ricardo Vaz Tê.
André Santos enters the game and replaces Ł. Podolski.
CHANCE! Arsenal have three against one here and Walcott tries to find either Cazorla or Giroud on the break but his final ball is poor and Demel has time to usher it away from goal. That really should have been six considering the options the England international had available to him there.
69'
West Ham have a free kick of their own now and Noble has it just outside the box on the left, but instead of having a crack at goal, he dinks it in and Koscielny nods clear.
68'
Says a lot about Walcott's status within the side that he was given that free kick moments before. Can't say I've ever seen him take one like that before.
67'
Delicious pass from Wilshere dinked over the entire West Ham back four sees Cazorla win a corner when his low cross into the box hits Demel.
66'
Arsenal have a free kick in a promising position around 30 yards from goal a touch to the left and Walcott steps up and gets his strike over the wall but it;'s straight at Jaaskelainen.
65'
Gibbs is jaunting down the left with a real spring in his step. To be honest, given Guy Demel's display tonight, I would be too.
64'
For the first time this half the visitors are actually enjoying a small spell of possession but it all comes to an end when Noble's ball out wide to Demel has too much on it and goes out for a goal kick.
63'
D. Potts enters the game and replaces J. Collison.
Potts tries to fashion some space for himself down the left but Sagna doesn't give him any breathing room and wins a throw-in for his troubles.
62'
A. Diarra enters the game and replaces W. Reid.
61'
Some serious middle class cheering from the Arsenal fans as they win yet another corner. All very polite and proper. No escape for West Ham at the moment.
60'
No relief for West Ham as Walcott wins a corner down the right, Wilshere steps up and curls a dangerous ball into the near post but Tomkins heads clear.
59'
Absolutely mad start and West Ham are getting bodies forward as Vaz Te puts it wide from an offside position after trying to get a toe onto Noble's volleyed ball over the back four.
58'
L. Koscielny enters the game and replaces T. Vermaelen.
57'
O. Giroud has scored a goal for Arsenal! Assist by Ł. Podolski.
GOAL! Can you believe it? Arsenal have bagged their fourth of the half as they break away at pace with Cazorla spraying the ball out to Podolski who delivers a pacy delivery into the near post for Giroud to turn home on the run. Where has Guy Demel gone? West Ham have just collapsed here.
55'
CHANCE! Tomkins goes on a mazy run up the pitch and breaks into the box before laying it off to Cole, who sees his tame strike easily held by Szczesny.
54'
T. Walcott has scored a goal for Arsenal! Assist by Ł. Podolski.
GOAL! West Ham are suicidally high up the pitch as Wilshere wins the ball and plays it into Podolski in acres of space down the left and his first-time ball right across the box from the touchline sees Walcott run onto it at pace before finishing with aplomb past Jaakselanin without even breaking his stride. Magnificent move.
53'
Santi Cazorla has scored a goal for Arsenal! Assist by Ł. Podolski.
GOAL! A truly brilliant team goal hands Arsenal a 3-1 lead as Podolski on the edge of the box plays it into Giroud, who delivers a first-time ball over the top to the forward, who then looks up and rolls it across the box for Cazorla to backheel into the net. Cheeky finish.
52'
CHANCE! Much better from Cazorla and Walcott wriggles free of O'Brien again down the right as he breaks into the box, but under pressure, the ball is cleared by Reid.
51'
That's the side of Arsenal manager Arsene Wenger won't want to see this half, as Cazorla overplays it and knocks the ball out of play when a simple pass was on had he just taken a touch first. No flash needed when you're in this much control.
50'
Podolski just about offside as he collects Cazorla's slide rule pass at pace down the left flank. Dangerous times for the visitors right now.
49'
West Ham can't get anywhere near the ball at the moment as Taylor goes in late on Ramsey on the halfway line.
48'
Fantastic start from Arsenal here and they've began the second half just as they ended the first. Sam Allardyce will be livid.
47'
O. Giroud has scored a goal for Arsenal! Assist by T. Walcott.
GOAL! Giroud has put Arsenal ahead for the first time tonight after he darts ahead of his marker, Tomkins, to volley home on the stretch from Walcott's low corner at the front post. That looked like a move straight from the training ground.
46'
Arsenal get the second half going and Walcott is in behind just second after the restart, with Tomkins turning the ball behind with Wilshere lurking with intent close behind. Frantic start.
45'
Game just lacking that bit of tempo now as both sides look seemingly content to go at half time level.
Cazorla wins a free kick after Nolan shoves him over in a decent position wide on the right....
CHANCE! It's a fabulous effort from Cazorla as he curls his left-footed free kick into the top corner but Jaaskelainen gets something on it and after a goalmouth scramble, Giroud sees a strike on goal kncoked behind for a corner. So close.
44'
Mertesacker knocks it long and Giroud wins the ball in the air yet again, with the hosts coming away with the ball as they seek to create one last opportunity before the break.
43'
Ricardo Vaz Tê gets yellow.
Arsenal have registered 68% possession this first half yet were it not for a clearance off the line just now, they could be a goal behind. Tells you everything you need to know about how fragile this side are.
41'
CHANCE! West Ham nearly pull ahead again after Demel's high cross into the box is deflected into Cole's path courtesy of a poor Sagna header which strikes Nolan, and the striker sees his clipped effort cleared off the line by Ramsey.
40'
The hosts shift the ball around the pitch well before Cazorla finds himself in space 30 yards from goal, but he drags his effort well wide. The Spaniard hasn't quite found his range just yet tonight.
38'
West Ham are firmly camped in their own half at the moment, offering little to no threat.
37'
Wilshere comes away with the ball after a tussle with Demel and as he looks to play the ball behind through to Walcott, Tomkins gets a crucial toe to the ball to divert its path away from the forward and to O'Brien to mop up.
36'
CHANCE! Absolutely brilliant flowing move involving Giroud, Gibbs and Podolski sees the left-back cut the ball across the box to the Germany international, but it falls to his right foot and his scuffed effort is hoofed clear by O'Brien. Champagne stuff, that.
34'
Noble has the ball in space in the middle before Wilshere is on him in a flash, nipping at his toes. It's that sort of energy that Arsenal have been seriously missing these past 18 months.
32'
Giroud wins the ball in the air and Cazorla picks it up before going on a mazy run down the right, with Reid getting his body to turn the cross behind for a corner.
31'
West Ham win a free kick on the right and Taylor swings in a vicious ball only to see it fly out of play without a touch.
30'
Superb play from Walcott as he skins Tomkins for pace on the outside down the right before seeing his low cross hacked clear by Reid.
29'
Wilshere is popping up everywhere at the moment as he sees an effort deflected straight into the arms of Jaaskelainen from the edge of the box.
28'
That midfield areas looks extremely congested at the moment and West Ham just can't get a foot on it to try and impress some sort of control on proceedings. Arsenal are first to every ball at the minute.
26'
Gibbs and Wilshere work the ball out to the left wing where Giroud whips in a cross to nobody. Ironically, that's exactly the sort of delivery the Frenchman thrives on.
25'
Vaz Te goes in late on Mertesacker after the ball has gone out. Silly boy, people have earned themselves yellow cards for less.
24'
From Noble's delivery, Vaz Te climbs way above Sagna with a great leap before nodding the ball well over.
23'
This game has got a really lively tempo to it now as West Ham force a corner on the counter.
22'
Ł. Podolski has scored a goal for Arsenal! Assist by J. Wilshere.
GOAL! Wowzers we've got a game on here as Arsenal kncok the ball around with a bit more urgency and as Wilshere flicks it around the corner, Podolski finds a yard of space 30 yards from goal and hammers a ball into the bottom left-hand corner. Fantastic strike. Game on.
20'
Arsenal look a bit shocked at going behind in a game they've dominated possession in up until now. They're still stroking the ball around nicely but lacking that crucial killer touch in the final third.
18'
J. Collison has scored a goal for West Ham United!
GOAL! Taylor's ball in sees Reid go close at the near post with another corner forced, but from the next delivery, Vermaelen nods clear and Collison collects the ball on his thigh before rifling the volley past Szczesny into the net. West Ham are 1-0 up.
16'
CHANCE! After Tomkins pumps another long free kick into the box after Gibbs fouls Demel, it causes confusion in the Arsenal box and Taylor sees his effort deflected just over the bar with Szczesny scrambling.
15'
CHANCE! What a superb last-ditch challenge from Reid that is as he snuffs out Walcott's effort after the striker latches on to a fantastic through ball from Wilshere. Looked a corner but a goal kick has been given.
14'
West Ham still chasing the ball for the most part but Nolan has started to drop deeper to help out Noble when they do have possession.
13'
Some fluid play down the left flank almost sees Giroud lay the ball off in the box to Podolski before Reid gets across to poke clear. When the ball is worked around the midfield towards the edge of the box, Cazorla then blazes an effort miles over the bar.
12'
O'Brien laucnhes another long ball into the box and Mertesacker just about gets above Cole to clear. Something tells me the Germany international is going to be awfully busy tonight.
11'
A long punt forward from Tomkins sees Nolan latch onto the ball before playing it back to Demel, but his cross lacks power and Vaz Te's header is glanced harmlessly wide.
10'
After the hosts win a corner down the right after some fine work from Sagna and Walcott, Wilshere's corner is easily dealt with by West Ham.
9'
Roy Hodgson is watching on from the stands tonight and it looks as if Wilshere is going to be alright to continue as he limbers himself up on the sidelines.
8'
Wilshere is down after Collison goes over the ball and in on the England international's ankle. That looked a bad one on second viewing.
6'
Arsenal look in confident mood tonight as Cazorla steps over the ball before letting it run to Walcott. The move breaks down but a sign of things to come perhaps.
5'
Wilshere delivers a lovely pass down the outside of O'Brien and Walcott latches onto it before scuffing his low cross into the box. Waste.
4'
Our first long ball of the evening is hoiked into the box and when it breaks kindly to Demel, his cross on the right is deflected behind for a corner but Arsenal clear when it comes in.
3'
Noble intercepts and tries to release Cole on the break but Ramsey gets across for a neatly-timed cynical foul and the referee brings back play.
2'
Arsenal knocking the ball around in West Ham's half without any great purpose at the moment.
1'
And we're underway, with Andre Marriner our referee for tonight.
Good evening ladies and gentleman, my name is James McManus and I will be guiding you through events for tonight's play-by-play covering the game between Arsenal and West Ham at the Emirates.
The teams are starting to filter in and here is Arsenal's: Szczesny; Sagna, Mertesacker, Vermaelen, Gibbs; Ramsey, Wilshere, Cazorla; Walcott, Podolski, Giroud.
Arsenal subs: Mannone, Koscielny, Jenkinson, Santos, Frimpong, Oxlade-Chamberlain, Arshavin.
West Ham's starting eleven is as follows: Jaaskelainen, Demel, O'Brien, Reid, Tomkins, Noble, Taylor, Nolan, Collison, Vaz Te, C.Cole.
West Ham subs: Henderson, Potts, Diarra, Diame, O'Neil, J.Cole, Jarvis.
Time to tell you about the team news - Arsenal boss Arsene Wenger makes two changes to the side that featured in the 2-1 defeat against Chelsea, with Aaron Ramsey and Lukas Podolski coming in for Abou Diaby (illness) and Francis Coquelin, while Alex Oxlade-Chamberlain has overcome illness to take his place on the bench.
West Ham boss Sam Allardyce makes four changes to the side that drew against QPR last weekend, with Matty Taylor, Carlton Cole, Ricardo Vaz Te and Jack Collison all drafted into the side and Joe Cole, Matt Jarvis, Mohamed Diame and on-loan Arsenal striker Marouane Chamakh making way.
If you're wondering why Chamakh won't be playing for West Ham tonight, it's because he's ineligible as part of his agreement with his parent club, Arsenal.
A few factoids to bring you now: Arsenal are unbeaten in their last 10 league and cup games against West Ham, winning eight of those matches.
West Ham have claimed just eight points from the last 30 available, and have lost four of their previous five away league games. They've also scored just five goals on the road this term.
The Gunners are yet to lose a game in which they have taken the lead this season, winning seven and drawing two.
Both clubs will be enjoying their second London derby in a row this evening too, with Arsenal having played Chelsea at the weekend and West Ham drawing at home to QPR.
We're moments away from kick-off at the Emirates now, with all of the players out on the pitch. My prediction is 3-1 to the hosts.
Referee Andre Marriner brings a close to the first half at the Emirates after Matty Taylor's free kick is fired in low straight at Szcesny from distance and it's Arsenal 1-1 West Ham at the break.
That was a hugely entertaining half of football from both sides with a great ebb and flow about the game so far. Arsenal have responded well to going behind but they still look extremely vulnerable from corners and set-pieces.
So what will Arsene Wenger be demanding of his side aafter the inveral? More of the same will be the order of the hour but perhaps just a shade more movement from the likes of Giroud and Podolski up top, with Walcott the only one finding gaps in the visitors defence at the moment.
For West Ham, the gameplan has worked so frar, namely getting men behind the ball in their own half and trying to catch Arsenal on the break and at set-pieces. They nearly went ahead with Carlton Cole seeing his effort cleared off the line from Aaron Ramsey.
With regards to both goals, while Collison and Podolski did well to pick out two such magnificent strikes, each side will be disappointed with the way they closed the ball down before the goal flew in.
My prediction of 3-1 is still on for Arsenal, but they'll need to step it up a notch after the break.
The players are back out on the pitch, we're moments away from getting back underway at the Emirates now.
Andre Marriner brings an end to the game and Arsenal move up to fifth in the league after beating West Ham 5-1 at the Emirates. The Hammers have been well and truly hammered tonight.
That blistering 15-minute period after the break at the start of the second half saw Arsenal put this game to bed with a flurry of four goals and some clinical finishing on show.
Well folks, that brings an end to our live play-by-play coverage for tonight, so thank you for joining me as we witnessed Arsenal get close to something approaching their best against a poor West Ham side to the tune of a 5-1 demolition. Stick around on site for all the best of the post-match reaction and I'll catch you all next time.
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