Andriy Yarmolenko stepped off the bench to hit the winner as West Ham shrugged off VAR controversy to beat Chelsea 3-2 and give their Premier League survival hopes a huge boost
 The Hammers had controversially been denied an opener when Tomas Soucek's strike was scrubbed out by VAR but battled back from Willian's (42) penalty to lead when Soucek (45+2) and Michail Antonio (51) netted either side of the break
However, a superb free-kick from Willian (72) looked to have shared the points until West Ham broke away and Antonio teed up Yarmolenko to cut past Antonio Rudiger to fire home in the 89th minute
That goal sealed just the third win of David Moyes' second tenure at West Ham and lifts the Hammers three points above the relegation zone with six games remaining
Chelsea, meanwhile, will be frustrated at failing to capitalise on  earlier in the day, when a win in east London would have moved them up to third
With only goal difference keeping West Ham out of the relegation zone at kick-off, they were pushed back early on by Chelsea, with Marcos Alonso and Willian hitting the target for the Blues, who were wearing their new home shirts
But Antonio was a threat on the break and should have done better when he scuffed wide on 13 minutes
 Pulisic then blew a good chance of his own at the other end, curling over from 15 yards out as Chelsea resumed control
However, it was West Ham who thought they'd taken the lead against the run of play on 34 minutes when Soucek finished off a goalmouth scramble - but after three and a half minutes of deliberation, VAR ruled the floored Antonio was offside
Chelsea rubbed salt in West Ham wounds by winning a penalty at the other end moments later when Pulisic was too slick for Issa Diop and Willian made no mistake from the spot
But West Ham refused to be denied and from another corner, Soucek once again got the better of Cesar Azpilicueta at the back post and headed the hosts level seconds before the half-time whistle with his first goal for the club
West Ham began the second half impressively and within six minutes of the restart completed the comeback when Antonio - who had a good penalty appeal against Rudiger in the build-up - slammed home Jarrod Bowen's low centre
But hopes of a vital win were short-lived, and when the standout Pulisic was brought down on the edge of the box Willian whipped a fantastic free-kick in off the post - although Lukasz Fabianski's positioning on his side of the wall looked questionable
Sub Jack Wilshere - making his first appearance since October - played in Antonio for a one-on-one but Kepa Arrizabalaga was out well to deal with the danger before Chelsea replacement Olivier Giroud mis-kicked at the vital moment at the other end
There was no mistake from Yarmolenko though
 The ice-cool Ukrainian - who had left Alonso trailing - showed exemplary composure in the final moments to twist past Rudiger and fired past Kepa to grab three vital points for his side
Neither co-commentator , nor former Chelsea defender and studio guest  were impressed with Alonso's casual tracking of Yarmolenko for West Ham's late winner
Neville said: "Look at him, look at him! What are you doing, Marcos Alonso? There's his running back speed which has cost Chelsea the game
 Alonso is level with him at the point the counter starts
"He doesn't bother, that's why he's under pressure at this club and Frank Lampard will see that
 Run back as fast as you can when your team lose the ball, you learn that aged six
"Cole added: "One of the things I hate about full-backs is when you're happy to run back but not track
 I get they're pushing for it, last five minutes of the game, but you need a point here
 Could he have run back, could he have run back with the intensity he ran forwards? Probably, yes
 Could he anticipate earlier? Yes
"As players, you've got to want to work and not be happy to be beaten
 Alonso needs to get back quicker
 They've reacted too late, but first and foremost you've got to defend
": "I was spewing [at VAR]
"I was thinking: 'are we ever going to get a decision here?' Everything was going against us
 Some of the things that have gone against West Ham have been really poor
 I can't explain it
 I said to the player that we need to make our own luck and it went our way tonight
 We pushed hard and did a lot of good things - the players deserve a huge amount of credit, they are sticking to it and got their rewards
"We'd be lying if we said we weren't looking at the results, of course we are
 But I hadn't thought we had been as bad as the results suggested, we'd lost 2-0 in both, but I thought the teams we played had played well and we made a couple of mistakes
 Tonight we took most of the chances
""I wouldn't say it's the story of our season because it's been a good season
 But there have been so many of these moments
 I explained it clearly to the players before the game: we had a good restart, three good results, and an opportunity today to go third
 But you have to do every part of the game to get results in games like this
"You can dominate possession, which we did for most of the game
 But if there are moments where you switch off, if you go 1-0 up and then make two or three errors to them scoring and going 1-1 before half-time, you're going to encourage teams on
"It's been there and I'm very aware of it, but the players in those moments have to show an extra mentality, an extra bit to do the bits that see a game through like this when you have a lot of domination
"Chelsea host Watford on Saturday - from 7
45pm on Sky Sports Premier League - while West Ham travel to Newcastle on Sunday - from 2pm on 
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