Mikel Arteta admitted Arsenal were “extremely poor” and struggled to react to setbacks in their 2-0 defeat to PSV Eindhoven.
The Spaniard said a first defeat in 10 games meant his side need a “reset” ahead of their meeting with Nottingham Forest on Sunday.
Joey Veerman and Luuk de Jong scored for PSV as Arsenal missed the chance to win Group A and may now need to beat FC Zurich at home next Thursday to avoid an extra round of the competition in February.
Arteta said: “It’s the end of a long run and now it’s time to reset and analyse what happened. PSV deserved to win, no question. We were nowhere near our level today.
“Last week the game was all ours. Today it was very different and when you play like that against the top teams it’s very difficult to win. Today we were extremely poor.
“There have been periods recently when we have been excellent and others when we have suffered. We’ve not had the consistency for 95 minutes that we want.
“We didn’t have the threat and aggression we’ve been playing at and that is worrying. The moment something went wrong we just went down and didn’t know how to react.
“It’s my responsibility to get the best from the players. They have been exceptionally good and playing at a level that probably no one expected. Now it’s down to me to get the best out of them.”
