By Chris Harris

Arsène Wenger has described Manchester United's Champions League exit as "an accident" but he believes the margin for error in the group stage is smaller than ever.

The 2011 finalists tumbled out of this season's competition after a 2-1 defeat at Basel on Wednesday night and will join their city rivals in the latter stages of the Europa League instead.

Wenger was as surprised as anyone to see United slip up but, having navigated his own team's path through a tricky group, the Frenchman believes the standard of opposition is on the rise.

"It's difficult to believe [the Manchester clubs are out] but that's reality," Wenger told Arsenal Player.

"We spoke earlier in the season about the margin between English Premier League clubs and the rest becoming smaller. That means we all live on a smaller margin and if you have one or two players injured or lose a game with bad luck, you go out."

The Manchester clubs are leading the way in the Premier League but Wenger is not sure how their switch to Thursday night European football will affect the title race.

"It's difficult to predict right now," he said. "When you go out of the Champions League it is of course a big disappointment but every team responds in a different way.

"You want to play in the Champions League but the risk is that you have to go out at some stage. You have to deal with the disappointment, that's part of being a big club.

"Let's not forget that Manchester United have played in three finals out of the last four, so for them we have to consider it [their exit] as an accident."

Watch the full interview with Wenger on Arsenal Player.

Copyright 2014 The Arsenal Football Club plc. Permission to use quotations from this article is granted subject to appropriate credit being given to www.arsenal.com as the source 9 Dec 2011