Andy Carroll's hat-trick dealt a fresh blow to Arsenal's faint title hopes as West Ham held them to a thrilling 3-3 draw on Saturday.
The Gunners looked on course to keep in touch with leaders Leicester when Mesut Ozil and Alexis Sanchez struck inside 35 minutes to put the visitors in firm control at Upton Park.
Carroll's treble inside 10 minutes either side of the interval turned the game on its head but though the towering forward might have given England boss Roy Hodgson food for thought, the Hammers had to settle for a point as Arsenal captain Laurent Koscielny hit back (70).
The result does little for the sides' respective title and top-four aspirations, Arsenal 10 points adrift of leaders Leicester, having played a game more, and West Ham still in sixth, two points off the Champions League places.
Slaven Bilic's side almost made the perfect start as Manuel Lanzini headed Aaron Cresswell's scuffed volley wide inside the opening minute, although the effort would have been ruled out for offside.
The Argentine was the hosts' biggest threat in a cagey opening and he was unfortunate not to have opened the scoring when, having found the back of the net, linesman Darren Cann wrongfully ruled out his header for offside on 13 minutes.
Arsenal posed a constant threat and, within five minutes, they took advantage of their reprieve as Alex Iwobi played Ozil through to slot past Adrian.
The opener rattled West Ham, who were restricted to a couple of long-range free-kicks from Dimitri Payet, as Iwobi turned provider again, releasing Sanchez who made no mistake in doubling the Gunners lead with a low finish 10 minutes before the break.
Having turned Laurent Koscielny on the edge of the area, Carroll looked to halve Arsenal's lead immediately but David Ospina was alert to keep his low out as the Gunners coasted towards the interval.
But their lead was eventually snatched in an emphatic 160-second spell from West Ham.
First, Carroll outmuscled Nacho Monreal at the far post to head Cresswell's cross beyond the stricken Ospina on 44 minutes, before the turnaround was completed in stoppage-time with a thunderous left-footed volley.
The half-time whistle momentarily spared Arsenal from the ensuing West Ham onslaught, but it was back underway in the second half.
The hosts saw half-hearted penalty claims ignored by referee Craig Pawson following Hector Bellerin's clumsy challenge on Lanzini, before they were then denied a third goal as Carroll was penalised for a foul on Koscielny in the build-up to Payet capitalising on defensive hesitancy.
The Gunners, though, were unable to keep a rampant West Ham side at bay and the pressure finally told as Carroll complete his hat-trick on 52 minutes with another assured header at the far post after Michail Antonio's cross from the byline.
Carroll had the chance to extend his side's lead further, but his failure to convert Payet's cross opened the door for Arsenal to drag themselves off the canvas.
Monreal almost put an indifferent defensive display behind him by levelling the tie on 68 minutes, only for Lanzini to clear his effort from the edge of the area off the line.
That chance marked a change in the tide at Upton Park as Arsenal, boosted by the addition of substitute Olivier Giroud, applied the pressure and got the breakthrough through Koscielny's smart finish after another assist from Ozil.
With both sides fighting back from losing positions neither risked losing a point in the closing stages as the spoils were unsatisfactorily shared.
West Ham: Adrian (7), Tomkins (6), Reid (7), Ogbonna (6), Cresswell (8), Kouyate (6), Noble (7), Lanzini (7), Antonio (8), Carroll (9), Payet (7).
Used subs: Emenike (6).
Arsenal: Ospina (6), Bellerin (6), Gabriel (6), Koscielny (7), Monreal (5), Elneny (7), Coquelin (6), Iwobi (9), Ozil (7), Sanchez (7), Welbeck (8).
Used subs: Giroud (6), Walcott (5), Ramsey (5).
Man of the match: Andy Carroll