West Ham knocked out Manchester United in the third round of the Carabao Cup with Manuel Lanzini's early goal enough for a 1-0 victory.
Ole Gunnar Solskjaer's side were beaten semi-finalists in the last two editions and came into this match fresh from sealing a thrilling 2-1 Premier League win at the London Stadium when the sides met on Sunday.
But three days on, it was David Moyes' men celebrating as Lanzini secured West Ham a rare Old Trafford triumph and Carabao Cup progress as the hosts failed to turn 27 shots into a goal.
The Hammers had failed to win on their previous 17 trips to Old Trafford, with Carlos Tevez the last player to score a winner there back in May 2007.
This time, Argentine compatriot Lanzini did the damage, sweeping home after Ryan Fredericks roared past a rusty Alex Telles on a night when the sides made a combined 21 changes.
West Ham will now face Manchester City in the last-16.
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Dean Henderson made his first appearance of the campaign having struggled with prolonged fatigue after contracting Covid-19 and Telles was another making his first start of the campaign.
The Man Utd left-back looked rusty on his return from an ankle injury and was breathing a sigh of relief after Jarrod Bowen missed the target following his poor attempted challenge.
West Ham debutant Alex Kral saw a close-range shot blocked by Eric Bailly as the Hammers continued brightly, with Moyes' men capitalising on out-of-sorts Telles in the ninth minute.
Fredericks' burst beyond the left-back and his deflected cutback from the byline was struck beyond Henderson by Lanzini in front of the Stretford End.
It appeared to act as a wake-up call for the hosts and Sunday's match-winning goalscorer Jesse Lingard was furious referee Jon Moss did not award a penalty.
The former West Ham loanee went down in the box under pressure from Mark Noble, who was being teased by home fans after David de Gea saved the substitute's late penalty on Sunday.
Jadon Sancho saw a shot blocked and Anthony Martial sent a deft touch bobbling wide after Juan Mata's cross-shot rattled the crossbar as the home side launched wave after wave of attack.
But, despite being under the cosh and forced to replace injured Fredericks with Vladimir Coufal, West Ham retained their lead heading into the break as Alphonse Areola denied Lingard before Telles and Martial failed with attempts.
Solskjaer's side returned from the break strongly and Mata delightfully clipped over for Sancho to hit an audacious volley from an acute angle off target, before Diogo Dalot rifled a low effort just wide.
Andriy Yarmolenko struck wide from 20 yards as West Ham threatened to extend their lead, with Solskjaer turning to substitute Mason Greenwood - a move that almost paid immediate dividends as he forced Areola into a smart stop.
The West Ham shot-stopper denied Lingard before Solskjaer introduced Anthony Elanga and Bruno Fernandes as the hosts attempted to turn the screw.
The latter bent wide from 25 yards and Areola blocked Martial as the match entered the final 10 minutes, with Man Utd leaving gaps at the back as they searched for a leveller.
Yarmolenko somehow hit the post having rounded Henderson in the 86th minute and two minutes later Noble was played in by Bowen, only for his first-time strike to be stopped by Henderson.
The Man Utd goalkeeper denied Bowen soon after but those missed chances did not prove costly as West Ham celebrated.
What the managers said
Ole Gunnar Solskjaer said: "It was a poor start again, that needs addressing. After that we played well for long periods and gave it a good go. Stats don't mean anything but when you've got 27 shots you know the boys have given it a good go.
"We didn't create big chances but we created pressure. Mason Greenwood had a big chance but sometimes that pressure doesn't come to anything. Of course, in the last few minutes we had to go gung-ho and they could have scored another.
"You want to go through but it's a long season. Everyone gave it a good go. I can't fault their attitude. We've got big games coming up and that's the decision we made.
"We're at the start of the season, we know it's going to be a long journey. Champions League, FA Cup, Premier League - we've got lots of games. We just keep doing what we're doing to try and get results. We've started the season OK, apart from being out of this cup, which isn't great. And we haven't had a good result in Europe but we'll be ready for Saturday."
West Ham first-team coach Stuart Pearce said: "Obviously we're delighted with the result.
"It's a really tough place to come.
"We had to sustain pressure for periods of the game but I think we started the game very well, deservedly got in front and at the end of the game potentially could have two goals and maybe make the evening a little bit more comfortable for us bystanders in the stand.
"We're delighted, we got real togetherness at this football club, and the players were fantastic tonight.
"We were really disappointed we didn't get something for the weekend.
"I think on the day we were at least worthy of a point so we're disappointed with that but United are an outstanding team, with a lot of talent within their group.
"We're just aspiring to challenge the likes of United but the way the manager has got this club going and pulling for each other and a real togetherness, from the terraces right the way down, is absolute credit to David, really."
Manchester United host Aston Villa in the lunchtime kick-off on Saturday; Kick-off at 12.30pm.
West Ham are back in the north on Saturday for their next game when they travel to Leeds on Saturday; Kick-off at 3pm.
Carabao Cup 2021/22 schedule
- Fourth round: October 26 and 27
- Quarter-finals: December 21 and 22
- Semi-finals: January 4/5 and 11/12
- Final: February 27