Henrikh Mkhitaryan could be unavailable for the second leg of the Europa League semi-final against Atletico Madrid, according to Arsenal manager Arsene Wenger.

Mkhitaryan netted the equaliser in Sunday's 2-1 Premier League defeat at Old Trafford, the Armenia international becoming the first player to score both for and against Manchester United in the same Premier League season. 

But Mkhitaryan was forced off in the second half after suffering a knee problem, with Wenger confirming goalkeeper David Ospina and midfielder Alex Iwobi also sustained injuries in the game.

"Mkhitaryan had a little knock on his knee," Wenger told a post-match media conference.

"Ospina has a rib problem. Iwobi has a hamstring problem."

Asked if the trio will definitely miss the Atleti game, he said: "At the moment, no. We will monitor them."

Wenger has yet to confirm his plans, the Frenchman having announced he is leaving Arsenal at the conclusion of the campaign to end a near 22-year stay at the club.

But the 68-year-old said he does not expect to be back at Old Trafford next season locking horns with old rival Jose Mourinho - who, along with former United boss Alex Ferguson, presented Wenger with a pre-match gift.

"At the moment I am a bit in unknown territory," Wenger said. "Will I take a break? I would be surprised if I see him [Mourinho] next year.

"I am programmed to win games, that doesn't change. I am grateful to Manchester United.

"It was very classy from them. It's the first time I get a trophy before the game."

Wenger named his youngest Gunners XI since an infamous 8-2 defeat to Ferguson's United at Old Trafford in 2011, with Greek defender Konstantinos Mavropanos impressing on his Premier League debut.

"My successor will watch this game today," Wenger said. "Hopefully he will come to positive conclusions. Some of the young players have shown they can handle it, 100 per cent.

"[Ainsley] Maitland-Niles is slowly getting to be the player I think he can be. He creates as well. Mavropanos in training has shown top quality. Can he show that in a big game? You never know. I think he did. He surprised everyone with his quality today.

"There were many question marks before the game. The quality of our game was good, individually players stood up. It was negative result but a positive performance.

"We had a very young team. The players are destroyed in the changing room. They gave everything."