Arsenal boss Arsene Wenger explains 5-1 defeat to Bayern Munich

Arsenal manager Arsene Wenger says his side's mental collapse was the reason behind their humiliating defeat to Bayern Munich in the Champions League last 16 at the Allianz Arena. The Bundesliga leaders inflicted upon the Gunners a second 5-1 loss in as many seasons after the visitors fell apart after half time.

Arjen Robben's stunning opener was cancelled out by Alexis Sanchez's goal in the opening 45 minutes; a half during which the north London side could have taken the lead after Granit Xhaka and Mesut Ozil were denied by Manuel Neuer. Captain on the night Laurent Koscielny went off injured after the break and the loss was the catalyst for a stunning demise.

Robert Lewandowski headed home and Thiago Alcantara struck twice, the second a deflected strike after a half-cleared corner, all within 10 minutes before substitute Thomas Muller fired home as the wheels came off the Arsenal display. Wenger was at a loss to explained the result, but says a lack of mental fortitude saw Bayern run away with the win.

"It is difficult to explain," the Arsenal boss told BT Sport. "Just before half time we had two good chances to score at 2-1. We came back and played well. We were unlucky on the second goal because gives a corner for us and the ball is on the pitch and they play with a second ball and we have four players up.

"We concede the second goal and that is one. In the second half the most important we lost Koscielny very quickly, who came off at 1-1 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 were a bit unlucky as well. Well done Bayern they were better than us.

"I do not look for excuses. I look for an explanation. We were quite solid defensively and after that of course it is very difficult. It is a shock to lose like that at this level and on top of that we have done everything wrong, the fifth goal shows that.

"We were [in control] but these kinds of games you need something in your side and be focused for 90 minutes. I felt the third goal was a killer for our players, after that we had no response. We have to recover and focus on our next game."

Non-league Sutton United host Arsenal in the FA Cup fifth round next Monday [27 February] in the club's next game, but it is not yet known whether Koscielny will be available. The France international was replace after 48 minutes with an ankle problem and the extend of the damage is yet to be confirmed.