Bayern thrashing raises further questions about future of arsenal's longstanding manager.

Arsenal manager Arsene Wenger conceded his team had “collapsed” in the second half of their 5-1 defeat to Bayern Munich in the Champions League on Wednesday.

Arsenal were level 1-1 at half-time but three second half goals in the space of ten minutes after captain Laurent Koscielny limped off with a hamstring injury, effectively ended the tie as a contest. A fifth goal in the closing minutes merely rubbed salt in Arsenal’s wounds.

Wenger, whose future whose future was already the subject of speculation as another Premier League title bid imploded after Christmas, said Koscielny’s injury was the turning point in the game.

“I think the most important in the second half [was] we lost Koscielny very quickly,” Wenger told BT Sport. “And suddenly it looked like we collapsed. Mentally, we collapsed, and overall I must say they are a better team than us as well.

“They played very well in the second half and we dropped our level. And we were a bit unlucky as well, but overall, well done Bayern. They were better than us.”

Alexis Sanchez had cancelled out Arjen Robben’s brilliant opener by scoring the rebound from his own missed penalty and Arsenal had chances to take the lead before the break, but Manuel Neuer denied both Granit Xhaka and Mesut Ozil.

However, after Koscielny limped off in the 49th minute, Bayern raced into a 4-1 lead courtesy of goals from Robert Lewandowski and two from Thiago Alcantara, before substitute Thomas Muller completed the rout in the 88th minute.

Wenger was unhappy that Bayern’s second goal came after the referee had initially given a corner to Arsenal but changed his mind, and Neuer took a quick goal kick while another ball was still on the pitch.

“The referee gives a corner for us. And the ball is on the pitch, they play with the second ball,” Wenger said. “Look, I do not look for excuses, I look for an explanation because we were quite solid defensively and after that, of course, it’s very difficult.

“In these kinds of games you need a bit of luck going in your side and you need to be focused for 90 minutes. I felt the third goal was a killer for our players because after that we had no response.”

Asked if the second half on Wednesday was one of the lowest points of his 21-year Arsenal reign, Wenger reefsued to discuss his own feelings.

“How I feel, I don’t think that is the most important,” he said. “But of course it is disappointing.”

Asked if Arsenal require a miracle to progress against Bayern, Wenger said: “Of course. I think we have to recover first and focus on our next game [against Sutton in the FA Cup on Monday].”