Mikel Arteta leapt to the defence of Alex Runarsson after the goalkeeper's nightmare evening deputising for No.1 Bernd Leno.
Runarsson, 25, produced a howler during the Carabao Cup quarter-final tie with Manchester City, letting Riyad Mahrez's tame free kick slip through his hands as the visitors went 2-1 up.
The shot-stopper's mistake proved to be the catalyst for City to run riot at the Emirates, as they added two more goals during a dominant second half to win 4-1 and progress to the semi-finals.
Runarsson was solid in four Europa League appearances but his display in his first real test will raise serious questions of his credentials as Leno's back-up.
Arteta insisted the Iceland international is still "adapting" to his new surroundings as he defended the player after the full-time whistle.
“He hasn’t played a lot of games for us, he’s just adapting to the league," said the Gunners boss. “We all make mistakes and we have to support him.”
Asked whether he would have liked to start Leno in goal, Arteta responded: “Yes, but as well we know that Bernd has played a lot of minutes.
“He needed some rest as well and we wanted to give opportunities to some other players. Alex has done well in the other games and these things happen in football.”
The Spaniard also claimed it would have been "impossible" for his side to emerge victorious from the cup tie in light of the costly error made by Runarsson, who joined on a four-year deal from Dijon last summer.
Assessing the performance, Arteta added: “A really hard one to take, considering how the game went, the reaction the team had against this level of opponent.
“Obviously when you give the goals away that we gave, you make the game impossible.”
Arsenal return to action with a Premier League clash against London rivals Chelsea on Boxing Day.
Was it a mistake to start Alex Runarsson instead of Bernd Leno against Manchester City? Have your say here.
Sign up to the Mirror Football email here for the latest news and transfer gossip.
