GOAL! A brilliant performance by Aguero is capped by another hat-trick. Great cross from the left, Bond comes out to claim it but gets nowhere near it and Aguero has an open net to head into. 4-2 and it's all over.
90' +2
City now just passing the ball around and waiting for the final whistle. Watford players look they want to leave now.
89'
Shame for Watford, they were brilliant in the first half and have tried to play on the counter this half but City have has too much quality. Zabaleta, Kompany and Jovetic have all been excellent since they came on and have really made a difference.
88'
Aguero has just been elbowed to the ground but Kevin Friend waves play on. Terrible decision.
87'
A. Kolarov has scored a goal for Manchester City!
GOAL! Kolarov has surely won it now! The corner is whipped in, it falls to Kolarov on the edge of the area and he hits it from 40 yards out through a host of players only for Bond to fumble it and see it trickle over the line. City fans do the Poznan!
84'
D. Fabbrini enters the game and replaces D. Faraoni.
Watford make another substitution. Diego Fabbrini replaces Marco Davide Faraoni, can he help them secure a replay? Zabaleta is fed down the right by Navas and wins a corner. Navas to take it.
82'
M. Cassetti gets yellow.
Kompany has been sensational since he came on. He began life at City as a central midfielder but Sven Goran Eriksson decided he'd suit the back four. He hasn't only played well but he's led his team brilliantly. Surely City will grab a winner now?
79'
S. Agüero has scored a goal for Manchester City!
GOAL! Aguero has done it again. He gets the ball on the edge of the area, puts it onto his left foot and fires it into the top corner. No chance for Bond. How good is the Argentine this year? He's on a Hat-trick.
76'
Game has gone a little flat but it's all City. Giuseppe Sannino has made another change to keep his side ticking over. Sean Murray is off for Almen Abdi. Can they hold on?
74'
A. Abdi enters the game and replaces S. Murray.
Jovetic has looked bright since he's come on. A lovely little one two with Dzeko almost creates an opening but Angella is there to cut it out.
Minute
Description
72'
Pellegrini will hope they can score two more, the last thing he wants is another replay down at Vicarage road. Aguero tries to slip in Dezeko through the middle but the Bosnian man handles the defender and gives away another free kick. Silly Eden.
70'
Navas again skips past Pudil and crosses to Dzeko, he tries to turn but is fouled and City have a free kick. The fans urging players to shoot whenever they have a sight of goal.
68'
FACT: Manchester City have played in two of the last three FA Cup finals. They won the trophy for the fifth time when they beat Stoke in 2011, but were beaten by Wigan in the final last season. They first lifted the FA Cup 110 years ago in 1904.
66'
The rain is coming down heavily now as the floodlights light up the wet soaked surface. Kompany is enjoying is central midfield position, flying forward whenever he can. It's like they have two Toures.
64'
The Etihad is really rocking now. They are expecting goals, they've got used to it. Watford still look dangerous on the break, but they can't get hold of the ball at the moment. Kompany on the edge of the area finds Aguero who side foots it toward goal but Bond easily saves.
62'
City are now well and truly on top. Watford are just trying to get a touch on the ball. Navas flicks it down the line to Zabaleta whose cross is out for a throw.
60'
S. Agüero has scored a goal for Manchester City!
M. Cassetti enters the game and replaces F. Forestieri.
GOAL! The pressure has taken its toll. Kolarov puts a quality ball in, Dzeko slides to meet it but Bond makes a good save but can only parry it into the path of Aguero who pokes it into the net. City are well and truly back in this game.
57'
S. Jovetić enters the game and replaces Rony Lopes.
Navas again does well down the right and wins a corner which he'll take. Jovetic is on for Lopes. The corner is cleared but only to Navas who drills the ball in toward Kompany and Jovetic who get in each others way and both fail to connect with the ball.
55'
Jovetic is about to come on. You'd expect he'll be replacing the young Lopes, he hasn't got into the game today. Despite that good start by City, Watford are now controlling the game again with some neat play in midfield.
53'
You get the feeling City are going through the gears and it's a matter of time before they score. Can Watford hang on? Well they have a corner, taken by Murray, it falls to Anya who shoots first time but it's a poor effort and Pantilimon collects.
50'
CLOSE! Another great set piece by City. Navas curls in the corner and Kolarov flicks it on but no one can get a meaningful touch. They have another corner after good pressing by Toure.
49'
Has Pellegrini ever had to give a half time team talk? Well whatever he said it's worked. City look a lot more threatening and are passing the ball quickly with intent.
48'
D. Pudil gets yellow.
47'
Pellegrini has made two changes at the break. Pablo Zabaleta replaces Micah Richards and Vincent Kompany is on for Jack Rodwell. Navas has just bee fouled on the far side and they have a free kick in a good position.
46'
V. Kompany enters the game and replaces J. Rodwell.
P. Zabaleta enters the game and replaces M. Richards.
We're back underway here at the Etihad.
45' +2
Lescott sums up City's half. He gets down the left wing and takes a big swipe at the ball with his left foot which goes out for a goal kick. Horrible play. Are these City players imposters?
45'
Just two minutes of stoppage time. Can City get a goal back? Rodwell tries to switch play from right to left but the ball whizzes off the pitch and Watford have a throw.
43'
The atmosphere is a little flat. The City fans are a little shell shocked to see an away side score goals this season. Watford still on top, quick one touch pasisng and it ends up with Deeney having a shot that hits the side netting.
41'
It's not a great effort, straight into the wall and Watford can break. Anya brings it away and passes it to Faraoni but Lescott dispossess him and the Hornets have a throw.
39'
Bond in the Watford goal clears it down field but City come straight back at them. Navas on the right hand side cuts it back to Aguero, who finds Richards but he's fouled and City have a free kick. Can they score before the break and start the comeback? Toure surely?
37'
They need some Silva creation. Navas the only City player looking dangerous, he whips in another cross but no one is there to meet it. City look so disjointed so far. Watford have a free kick in the centre circle.
35'
This is why it's so hard to win numerous trophies. Pellegrini has had to rotate the team today but it's just not working. Rodwell has been poor so far and Demichelis is just a constant liability. First time this season that City's squad players aren't performing.
33'
Rodwell and Deeney clash heads and there's a small injury delay. With half an hour gone, Watford look like they might be making the headlines this weekend. But it's fully deserved, they've been better than City in ever department. Worrying times for Pellegrini.
31'
City try and respond quickly, Ageuro finds space on the edge of the area and feeds Dzeko but the Bosnian's touch lets him down and he gives away a silly foul. City look shocked and very frustrated.
30'
T. Deeney has scored a goal for Watford!
GOAL! This is becoming a major shock! Deeney has put Watford 2-0 up here at the Etihad. Anya slips the ball through and again Demichelis is caught for pace, Deeney gets in behind the Argentine and pokes it past Pantilimon. How will City respond?
27'
Watford seem to have dropped a little deeper since they scored the goal. Not a good idea to let City come at you, because inevitably you will concede. But the Hornets don't look affected by the situation, maybe their visit here last January settled any nerves.
25'
Great ball by Toure which releases Aguero, he swivels and shoots in the box but it's deflected out for a corner.
23'
Forestieri is playing very well and looks buoyed by his goal. Clearly Watford's chief creator, he is zipping the ball about and making the City midfield look quite average. Navas slips by his marker but his delivery is straight into the hands of Bond.
21'
F. Forestieri has scored a goal for Watford!
GOAL! Would you believe it! City concede and it's Forestieri with the goal. He nips in down the left, beats Demichelis for pace and neatly slips it past Pantilimon. Quality stuff from the Argentinian and the game is now perfectly poised.
18'
City have scored 15 goals in their last three home games. If Premier League defences can't contain the Man City attack (they've already scored 106 goals this season in all competitions) then what chance do Watford have? So far, a pretty good one. The Hornets still looking good and have the ball.
15'
City try a training ground free kick, it almost works but Watford counter with Faraoni. It's four against two but Faraoni's pass is poor and Pantilimon claims the ball.
13'
Navas and Richards looking lively on the right side. Good play by them releases Aguero but surprisingly his delivery into the box is poor and Watford regain possession.
11'
CLOSE! Great delivery by Navas from the corner, Kolarov flicks it on and it races across the face of goal. Any kind of contact and City would be celebrating.
10'
E. Džeko gets yellow.
Quite a slow tempo to the game so far. The surface looks very soft and a few players look a little light on their feet. Watford are closing down City very quickly and have started the better of the two sides. City have a corner.
8'
Watford look very comfortable so far. Aguero gets his first touch of the ball and lays it off to Richards who is fouled and City have a free kick on the far side.
6'
Almost a big mistake by City as there is confusion between Richards and Pantilimon at the back. They get away with it and Watford have a throw in on the far side.
5'
Interestingly the FA Cup's joint top scorer is Britt Assombalonga who is currently on loan at Peterborough Utd from Watford. He's just scored another against Oldham. I wonder if the Hornets wish they had his goal scoring prowess today?
3'
Toure gives away a foul right on the edge of the City box. A host of Watford players rush over to take it but it's Murray standing over it. Straight into the wall but it falls to Faraoni who blasts over.
2'
Watford just passing the ball around and try to feed the ball through but Demichelis intercepts it and plays it away.
1'
And we're off, Man City kick off.
Hello and welcome to this afternoon's LIVE play-by-play commentary of the 4th Round FA Cup meeting between the Premier League's Man City and the Championship's Watford. My name is Greg Taylor and I'll be guiding you through all the action.
So with City in ominous form, winning 16 and drawing two of their last 18 matches, who expects Watford to sneak a heroic win? Well if there's a tournament that can throw up such a surprise, it's the old girl itself, the FA Cup.
Fresh from reaching the final of the Capital One Cup after their 9-0 thrashing of West Ham on aggregate, City turn their attention to another one of the four major trophies they are still in contention for as they host Watford at the Etihad.
Before we go any further, let's have a look at how both sides are lining up, starting with the home side.
MAN CITY XI: Pantilimon, Richards, Demichelis, Lescott, Kolarov; Jesus Navas, Toure, Rodwell; Lopes, Dzeko, Aguero.
MAN CITY SUBS: Hart, Kompany, Zabaleta, Clichy, Fernandinho, Nastasic, Jovetic.
Teenage striker Marcos Lopes keeps his place in the Manchester City side after a man-of-the-match performance against West Ham in midweek. He is one of six City changes as Edin Dzeko, Aleksandar Kolarov, Martin Demichelis, Micah Richards and Yaya Toure also come into the starting lineup.
Watford have made five changes to the side that drew with Bournemouth last time out. Jonathan Bond takes over from Manuel Almunia in goal, Lloyd Doyley is in for the suspended Fitz Hall, while Ikechi Anya and Fernando Forestieri also return to the side.
After last seasons excellent play-off campaign under Gianfranco Zola, Watford have had a harder time of it this season. They're currently in 15th position in the Championship and are on a poor run of results which has seen them pick up just two wins from their last 16 matches. One of those victories was their FA Cup third round replay victory over Bristol City.
The players are out on the pitch, we'll be underway shortly.
There's the whistle for half time. What will Manuel Pellegrini be saying to his players?
Watford thoroughly deserve their lead, they've passed the ball better, created more chances and scored two good goals. Can they sustain it for a full 90 minutes? After that showing you'd expect them to.
Surely City will crank up the pressure and mount a comeback. If Watford can weather the storm we may have another classic FA Cup shock on our hands.
The players are out on the pitch, we'll be back underway shortly.
And that's it. City complete another remarkable comeback and keep up their average of four goals at home this season. Ridculous, just ridiculous. Pellegrini made some inspired substitutions and when City had their best team out, Watford couldn't live with them.
The Hornets can be proud of their performance, but it'll be City who will be going into the 5th round of the FA Cup and keep up their hopes of winning an unprecedented quadruple.
That's it from me, Greg Taylor, thanks for joining us and have a great Saturday night.
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