Everton were stunned at home in their pursuit of a UEFA Champions League place with a shock 3-2 defeat to Crystal Palace.
After their victory over West Ham on Tuesday, momentum swung back towards Arsenal in the race for fourth place in the Premier League as Everton failed to match their rivals.
The Goodison Park fans would have been expecting an eighth straight home win in the league, but Palace had not read the script, with goals from Jason Puncheon, Scott Dann and Cameron Jerome giving them only a fourth away win of the season.
Palace looked dangerous throughout a frenetic game, in which Everton never got into top gear, and they took a deserved first-half lead through the in-form Puncheon - who notched his seventh goal of the season.
The advantage was doubled shortly after half-time by Dann's powerful header before substitute Steven Naismith halved the arrears with plenty of time remaining.
But Jerome's strike after 73 minutes re-established the two-goal cushion, and although a late Kevin Mirallas strike set up a nervy finish, Everton could not find a way back.
The hosts - who made three changes as part of an attacking line-up, with Ross Barkley, Mirallas and Aiden McGeady all starting - forced the pace from the off, with Gareth Barry stooping to head over from a Leighton Baines corner in the first minute.
Palace, though, soaked up Everton's early pressure and they looked dangerous on the break themselves.
They went closest to breaking the deadlock in the opening stages when, after 20 minutes, Jerome found space unmarked in the penalty area, but his header from Joe Ledley's cross flashed narrowly over the crossbar - although the Palace striker looked to be in an offside position.
The visitors made their pressure count after 23 minutes when Tim Howard could only parry Yannick Bolasie's right-wing cross. The ball fell to Puncheon, who finished neatly from 10 yards, for his fourth goal in the last three games.
It was nearly 2-0 before the interval when a breakaway saw Bolasie hit the base of the post from 30 yards, and an unbalanced Jerome could only put the rebound wide.
Romelu Lukaku then diverted a Barkley cut-back on goal, but Julian Speroni dived smartly to push the ball wide.
Ledley forced a fine save from Howard two minutes into the second half, but from the resulting corner defender Dann's powerful downward header stunned Goodison Park as it beat the unsighted goalkeeper to double Palace's lead.
McGeady almost responded immediately when his fierce 30-yard strike bent narrowly wide of Speroni's left-hand post.
Half-time substitute Naismith did pull Everton back into the game when he converted from close range after Baines had headed a deep Mirallas cross into his path after 61 minutes.
Mirallas then nearly equalised when he met a dipping cross from Baines at the back post, but with 17 minutes left Puncheon was again the architect with superb close control on the edge of the box, sliding the ball into Jerome, who curled into the bottom corner.
Everton refused to lay down even then, and with four minutes left Barkley's throughball was deflected into the path of Mirallas, who rounded Speroni and fired home.
But despite another late chance for the Belgian forward, who mis-kicked with the goal at his mercy, Everton could not find a way back as Palace hung on to effectively end any lingering fears of relegation, and simultaneously blow the race for fourth place in the Premier League wide open.
|Wolfsburg warn off De Bruyne suitors|
|Kone: I want to prove I can cut it at Everton|
|West Ham v Lusitans: Bilic set for first game in charge|
|Millennium Stadium to host 2017 UEFA Champions League final|
|Ronaldo a ´possibility´ for Portugal´s Olympics squad|
|Liverpool should get rid of Sterling - Grobbelaar|
|Miranda arrives for Inter medical|
|Arsenal can challenge the best - Cech|
|Real star Bale can be better than Ronaldo, says Keegan|
|UEFA approves changes to FFP rules|
|Honduras v Mexico: Moreno´s injury may force Mexican rethink pre-Gold Cup|
|Hiddink was the wrong man for Netherlands - De Boer|
|Vargas: I was scoring with every shot at training|
|Zambrano red rocked Peru - Gareca|
|Paraguay to change tack against Argentina|
|Sampaoli thrilled with substitutes´ influence, applauds Peru|
|Martino rues Copa America date with former side Paraguay|
|Former Birmingham City player Thwaites among Tunisia victims|
|Chile 2 Peru 1: Zambrano´s red card helps hosts into Copa final|
|Thiago Silva: ´I didn´t even know the ball had hit my hand´|
|Ronaldinho set to sign for Antalyaspor|
|Jara ban reduced on appeal by one match|
|Hiddink leaves Netherlands post|
|Cresswell pens new five-year deal at West Ham|
|Koeman: No serious United bid for Schneiderlin|
|Barbados eliminated from World Cup qualifying after fielding ineligible player|
|Former Catania president admits buying matches|
|Jones agrees Manchester United deal|
|Argentina v Paraguay: Valdez hoping not to need another comeback|
|Milan seal Bertolacci signing|
|Cech grateful to Abramovich and Chelsea fans|
|UEFA Champions League Preview: Brotherly pride at stake as B36 play TNS|
|UEFA Europa League Preview: Tommasi set to aid La Fiorita qualifying bid|
|Cech leaves Chelsea to join Arsenal|
|Paulinho ends Spurs frustration with Guangzhou move|
|Sampdoria confirm Eto´o exit amid Antalyaspor talk|
|Garcia departs Espanyol ahead of expected Qatar move|
|Watford to delay Doyley decision|
|Schlupp agrees new Leicester deal|
|Schweinsteiger hints at Bayern stay amid United links|
|Bertolacci thrilled ahead of Milan move|
|Langerak leaves Dortmund for Stuttgart|
|Muniain extends Athletic contract|
|Youngsters to get chance on US tour - Van Gaal|
|La Liga chief hits out at Real Madrid over TV rights opposition|
|Villa confirm Wilkins as assistant manager|
|Dicks joins West Ham coaching staff|
|Heldt enters to jeers, exits to cheers|
|Paraguay pride has grown at Copa America - Aguilar|
|Van Gaal tight-lipped on De Gea|
|Bacca confirms Milan agreement|
|Weight of expectation on hosts Chile to benefit Peru - Gareca|
|MLS Review: Timbers thump Sounders thanks to Adi´s double|
|Dzeko ´would run to Roma´ - Pjanic|
|Peru won´t sit back - Sampaoli|
|Zenga: Cassano, Balotelli will not be joining Sampdoria|
|Victory to start A-League defence away to Adelaide|
|I want to play MLS ´at the peak of my career´ - Johannsson|
|Allegri: I like Isco and Oscar|
|CAF Champions League Review: Comeback kings Smouha go top of Group A|
|Pirlo in attendance for New York derby|
|No Bayern deal yet, states Costa|
|Jara handed three-game ban|
|Sunderland striker Defoe sets 20-goal target|
|Leicester offer condolences to Albrighton and family after Tunisia attack|
|Chile v Peru: Potential Jara sanction hangs over semi-final|
|Sweden U21 v Portugal U21: History beckons for Jorge´s men|
|Neville appointed Valencia number two|
|Work halted at Olympic Stadium after fatality|
|Ibrahimovic in the same league as Messi - Sacchi|
|Giggs: United want to add winners|
|Turan sets record straight over transfer talk|
|Low keen for new Germany leaders to emerge|
|Tunisia part company with Leekens|
|Evans: Sterling´s Anfield exit must be a done deal|
|FIFA audit chief urges Blatter to stick by decision|
|Hrubesch urges caution after Germany U21s humbled|
|Taarabt hits out at ´very bad manager´ Redknapp|
|Bruce: I´m lucky I wasn´t sacked after Hull relegation|
|Van Hooijdonk warns Van Gaal over Depay tactics|
|SPFL looking into winter break|
|MLS Review: Earthquakes win California Clasico, Vancouver claim top spot in West|
|Muto must toughen up to succeed at Mainz - Ficcadenti|
|Diaz: Paraguay refuse to lose|
|Tragedy strikes for Paraguay match-winner Gonzalez|
|Robinho rues substitution, wanted to take penalty|
|Dunga: Brazil squad hit by virus|
|Fiorentina make ´insane offer´ to Salah|
|Women´s World Cup Review: England reach maiden semi-final|
|Mexico 2 Costa Rica 2: Herrera´s men recover after half-time|
|ES Setif 1 USM Alger 2: African champions beaten|
|Paraguay 1 Brazil 1 (4-3 on penalties): History repeats as Dunga´s men bow out|