The German champions trailed at half-time to Theo Walcott's goal in the 20th minute, but the game turned after the dismissal of Arsenal captain Koscielny for a foul on Robert Lewandowski in the penalty area and Bayern's top goalscorer converted the resultant spot kick.

"It was difficult game until we scored the penalty," Ancelotti said. "We had problems in covering positions well. Defensively we were too open and Arsenal pushed us hard as we expected. We should have had better control and our use of the ball was not as good."

In similar fashion to the first leg, when the French defender had to leave the pitch through injury, Arsene Wenger's side wilted as Bayern romped to the same scoreline as in Munich last month.

Further goals from Arjen Robben, Douglas Costa and a brace from Arturo Vidal, wrapped up a resounding 10-2 aggregate success over the hapless Gunners.

But according to Ancelotti, Bayern found it tricky coming to terms with their mammoth advantage from the first leg in Munich.

He said: "It is difficult to stay focussed when you are 5-1 up. We spoke about this before the game, but sub-consciously, you know you are 5-1 up and it's difficult."

Asked about his side's chances of winning the top prize in European club football, Ancelotti said: "We are really competitive. But in the Champions League little details decide games.

"Today we were suffering, then a penalty, sending off and the game was finished. It's really difficult to know what will happen in the future, but we are confident and competitive."

Ancelotti could allow himself the luxury of leaving Thomas Muller on the bench for 90 minutes as an unused substitute.

"I have only 11 players to play," Ancelotti said, when asked about the omission. "But he is very important for us and will help us the next game."