Despite the loss and hit to their top four hopes, United still have a chance of getting Champions League football next season.
Goals from Grannit Xhaka and Danny Welbeck in the second half saw the Frenchman claim his first ever Premier League victory when facing a team coached by the 'Special One'.
"I think the formation is good for the team", Gibbs told the club's website. I'm not enjoying that, honestly. "And Arsene Wenger is a big manager so my record (in never losing a Premier League game to him) is not normal". That is not normal. I really don't care about it today.
Xhaka's deflected goal helped Arsenal beat Manchester United 2-0 on Sunday, and a similar result at Southampton on Wednesday would take them above United into fifth place.
"Before when I left Highbury, they were crying, I left Emirates, they were crying". I leave the Emirates and they were crying - walking the streets with heads low. The Arsenal fans were finally cheering and singing and it is nice for them.
Eight changes to United's starting line-up at the Emirates Stadium certainly pointed to Mourinho's focus on Friday morning's semi-final, second-leg tie at home to Celta Vigo.
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With Kyle Schwarber up, Baez stole second to put the winning run in scoring position, but Schwarber struck out for the second out. Sale (3-2) reached double-digit strikeouts for the sixth straight time , stretching his major league-leading total to 73.
Mourinho however said he is does not enjoy seeing the north Londoners fail to win big trophies.
"Two days later Southampton, two days later Crystal Palace".
In 12 previous Premier League games against Mourinho the Arsenal boss had been unable to mastermind a victory, suffering five defeats and picking up seven draws. "It's up to us, we need some luck along the way, but if we win the next four games, I'm convinced that we can do it".
"We lost because we didn't score and we had great chances to".
The 19-year-old, who has been training with the Man United first team since January, made his first-team bow in the FA Cup against Wigan Athletic earlier this season, but his first taste of league action came away to Arsenal at the weekend. "When you play centre forward you know you want goals and so it hopefully gives him confidence", the 67-year-old said, speaking to reporters at the post-match press conference.
"We need everybody. We have such a small squad in this moment and these guys have a fantastic answer", he added.