A Kieran Gibbs own goal and a Wayne Rooney strike saw Manchester United return to the Premier League's top four with a bruising 2-1 victory at Arsenal on Saturday.
Arsenal subjected United's makeshift defence to heavy pressure throughout the game at the Emirates Stadium, but Gibbs's unwitting intervention gave the visitors a 56th-minute lead before Rooney added a late second.
Arsenal substitute Olivier Giroud marked his comeback from a broken leg by slamming home in the 95th minute, but United held on to leave their rivals 15 points adrift of leaders Chelsea in eighth place.
"It is the first away victory and the players are very excited, but it is just one victory," United manager Louis van Gaal told Sky Sports.
"We have to confirm that with further victories and then we can say we have the spirit and can start looking upstairs and not downstairs."
To compound matters for Arsenal, Arsene Wenger's side lost key midfielder Jack Wilshere and goalkeeper Wojciech Szczesny to injury, four days before an important Champions League home game with Borussia Dortmund.
"It was one-way traffic and we lost the game. We have to take it on the chin," said Wenger.
"We paid for the slightest mistake and it's very frustrating to come away with nothing."
United's injury blight obliged Van Gaal to deploy a three-man defence of Chris Smalling, Paddy McNair and Tyler Blackett, and the visitors then saw left-back Luke Shaw limp off after turning his ankle.
Arsenal peppered the visitors' goal with shots, but United goalkeeper David de Gea kept them at bay, notably thwarting Wilshere and Danny Welbeck, who was making his first appearance against the club he left in September.
Wilshere was forced off in the 55th minute after turning his right ankle in a challenge with McNair, and United struck barely a minute later.
Szczesny collided with Gibbs as he came for Ashley Young's left-wing cross and when Antonio Valencia drilled the ball back in, the prone Gibbs instinctively stuck out a leg, only to send the ball into his own net.
Szczesny had to go off, with Emiliano Martinez coming on, and the Argentine was a virtual spectator until Angel di Maria freed Rooney to run through and chip home in the 85th minute.
Giroud fired into the top-left corner from 20 yards mid-way through eight minutes of stoppage time, but United survived to give Van Gaal the first away win of his tenure.
Toure to the rescue
Earlier, Diego Costa scored again as Chelsea established a seven-point lead at the summit by comfortably beating 10-man West Bromwich Albion 2-0 at Stamford Bridge.
Costa scored his 11th goal of the season in the 11th minute, chesting down Oscar's cross and volleying home, with Eden Hazard adding a second before Claudio Yacob was sent off for a two-footed challenge on Costa.
"It was comfortable, but I thought in the first half we played amazingly well. In the first half we have to be 3-0, 4-0, 5-0 up," said Chelsea manager Jose Mourinho.
"But the quality of our football was there. I don't remember seeing many times football of that dimension."
Victory saw Chelsea set a new club record of 12 unbeaten games from the start of the season.
Mourinho's side are now seven points clear of second-place Southampton, who visit Aston Villa on Monday, and remain eight points above defending champions Manchester City, who won 2-1 at home to Swansea City.
Wilfried Bony put Swansea ahead in the ninth minute, but Stevan Jovetic equalised for the home side 10 minutes later and Yaya Toure strode through to score the winner early in the second half.
"We played very well and had a lot of chances to score the third goal, and we defended well," said City manager Manuel Pellegrini, whose side host Bayern Munich on Tuesday, knowing that even victory may not rescue their Champions League campaign.
Elsewhere, in-form Newcastle United climbed to fifth after Moussa Sissoko's 78th-minute strike earned them a 1-0 win at home to Queens Park Rangers - their fifth consecutive victory.
West Ham United dropped out of the top four after losing 2-1 at Everton, with Leon Osman sliding in the winner on his 400th club appearance after Mauro Zarate had cancelled out Romelu Lukaku's opener.
Burnley climbed off the foot of the table after Danny Ings scored twice in two first-half minutes to earn the promoted club a 2-1 win at Stoke City, who replied through Jon Walters.
Burnley are now level on points with fourth-from-bottom Leicester City, who drew 0-0 at home to Sunderland.