Jack Harrison scored a superb hat-trick as depleted Leeds produced a stunning 3-2 win at West Ham to dent the hosts' Champions League hopes on 
Harrison had not scored twice in the same game for Leeds in his previous 135 league appearances for the club, but he scored three times in the same afternoon to become their first player to net a league hat-trick against the Hammers since Russell Wainscoat in April 1927
Harrison put the visitors ahead with a precise finish as Leeds capitalised on their bright start (10) but West Ham levelled through Jarrod Bowen's ninth goal of the season after he met Aaron Cresswell's corner to head home (34)
It once more demonstrated the Hammers' prowess at attacking set-pieces, but they were undone when faced by one themselves just three minutes later as Luke Ayling's flick-on was nudged over the line by the unmarked Harrison
West Ham again rallied to level a second time seven minutes into the second half through Pablo Fornals' well-taken strike but Harrison would complete his hat-trick in style, latching onto the impressive Raphinha's through ball to lift his finish over Lukasz Fabianski (60)
The result derails West Ham's progress following three straight league wins, with Moyes' side remaining in fourth place on 37 points, two clear of Arsenal in fifth
Leeds' resurgence continues with this rare win in London coming after the 3-1 victory over Burnley as Marcelo Bielsa's side rise above Everton to 15th in the table, nine points clear of the relegation zone
Writing in his programme notes, Moyes highlighted how he wasn't too happy that the Norwich game in midweek had been sandwiched in between these two meetings with Leeds following that FA Cup win over Bielsa's side, claiming the players "prepared as well as they possibly could" as they dug in and showed resilience to claim three more points
By the final whistle, Moyes claimed the hectic schedule had caught up with his players
 He told : "I have to give credit to our players as to play Leeds one Sunday and then the next Sunday with the Premier League putting a game in between [vs Norwich] it's really difficult
 Leeds didn't have a game and we did
 Is it an excuse? Yeah, a little bit but I think it's a fair one
"When you play Leeds you know the intensity you need to play at - teams are glad to get Leeds out of the way
 We played them in the cup last week and got through
 We knew we had them in the league too but then the Premier League stuck the game in between
 It made it very difficult for us to play with the energy we needed
"We found it difficult to get prepared quickly but we had to do it
 We made the mistakes today, it wasn't anyone else's fault but there were other reasons for it too
"We've not been talking about fourth
 We've been talking about chasing the teams and we'll keep doing that
 The players are making a great go of it but today we were short and didn't play well enough
 But there are some mitigating circumstances for that
"Here, the Hammers looked somewhat disorganised in the opening period, certainly defensively, as they conceded two avoidable goals with Cresswell at least partially at fault for both
The left-back hesitated and allowed Raphinha to chase and win a lost cause before setting up Mateusz Klich to force Fabianski to parry the ball into the path of Adam Forshaw, who unselfishly teed up Harrison for a crisp finish
Stuart Dallas made a vital block to deny Michail Antonio before Cresswell would atone for his error to set up Bowen with a trademark set-piece delivery that found the stooping Bowen in between Pascal Struijk and Ayling to head beyond Illan Meslier
You sensed the hosts would build on Bowen's equaliser given that Bielsa saw his injury problems mount when both Forshaw and Junior Firpo were forced off with muscular injuries, but Leeds duly restored their lead before the break when Harrison was played onside by Cresswell to direct Ayling's knockdown into the net from close range
After the break, Moyes saw his team transformed upon the restart with Fornals hauling his side level for a second time when indecision from Ayling allowed Antonio to prod the ball into the path of the Spaniard to reverse his shot past the wrong-footed Meslier
Following Harrison's third of the afternoon, West Ham were handed a reprieve when referee Mike Dean consulted Craig Pawson to rule out Klich's strike from Raphinha's pull back after the ball struck the offside Rodrigo on the goal line
West Ham thought they had levelled when substitute Andriy Yarmolenko hooked his shot over the line from close range but Bowen was correctly flagged for offside in the build-up following Vladimir Coufal's shot
There was still time for Bowen to produce a glaring miss from Antonio's cross with virtually the final kick of a pulsating contest as he somehow chested over from underneath the crossbar - but it would have been rough justice on Leeds
"It's very frustrating" midfielder Declan Rice told  "We weren't like our usual selves
 We started the game poorly
 They were right on the front foot
 Their goal was a wake up call
"We are still in the top four at the minute
 This was a big chance to close the gap on Chelsea in second, but that is football
 It is about how you bounce back
"We always take it one game at a time
 We knew today was massive chance, it is a chance missed
 Massive
 There were silly mistakes today
"Bielsa's side were boosted by the return of Struijk while Rodrigo was named on the bench but their squad remained threadbare with nine other first-team players ruled out
Patrick Bamford, Kalvin Phillips, skipper Liam Cooper, Joe Gelhardt, Jamie Shackleton, Charlie Cresswell and Sam Greenwood remained unavailable, while Diego Llorente and Tyler Roberts were suspended
It meant 15-year-old Archie Gray was named on the bench for the second time this season - but Leeds rolled up their sleeves and produced a first-half display full of character, typified by Harrison
The 25-year-old has been a little slow to get going this term having scored eight league goals last season and only broke his duck this time around in the recent 3-1 win over Burnley, but he has rediscovered his scoring touch
Leeds could well have extended their lead before the break as Dan James was played through on goal by Raphinha but his shot was straight at Fabianski
 And yet, Bielsa would this time not be left to rue missed opportunities
His side could have buckled after Fornals' well-taken equaliser, but instead, Leeds wrestled control of this see-saw game once more as Dallas pickpocketed Vlasic to feed Raphinha before his perfectly-weighted pass was expertly finished by Harrison to complete his hat-trick
Raphinha came within inches of extending Leeds' advantage when his sublime free-kick crashed against the post, and while Bielsa did lament Klich's strike being chalked off by VAR, he would rise from his haunches to celebrate a breath-taking victory come the final whistle
"It was a typical Premier League game," Bielsa told 
 "It was good that it went in our favour but the margin was very close
 "It is a triumph for the players because of the effort they put in
 The desire to win was very, very big
"Bowen looked to the heavens at the death, missing when it was easier to score
 How costly it could prove to West Ham's Champions League hopes come May
Moyes added: "I'm not sure why he went for his chest rather than his head
 We shouldn't have been in that position in the first place, but for lots of different reasons we were
"Harrison told  "I'm delighted to get a hat-trick
 It is an amazing feeling to score and when you get three even better
 I am just really happy to take part in the win
"The last week we have been working super hard after the defeat against West Ham in the FA Cup
 We wanted to show a different side to us
 We were able to control the game a bit and get three points
"Hopefully we can go on a good run of form between now and the end of the season
"West Ham visit Manchester United at 3pm next Saturday at Old Trafford while Leeds United host Newcastle at Elland Road at the same time
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