Arsene Wenger believes Arsenal's defeat against Monaco is down to lack of mental strength.
After crashing out of the Champions League at the hands of European giants such as Barcelona, Bayern Munich and Milan in the last four seasons, the Gunners were handed a relatively easy tie against Monaco this season in the Last 16.
But despite missing key players, Leonardo Jardim's men were superior in all areas of the pitch as they take a comfortable 3-1 lead to the second leg at the Stade Louis II.
"We had a lot of possession tonight and I just believe that defensively we were not at the level," Wenger said after the game.
"Our weakness was more down to mentality. We rushed our game, we knew coming back at half-time it was important not to concede a second goal and we were too impatient.
"This is a game of 180 minutes and if you look at the second and third goal, it's difficult to explain how we conceded these goals. You cannot afford that.
"The players wanted to do well and come back when it was 2-1. They wanted to come back to 2-2 and forgot their elementary cautiousness.
"We have a smaller chance but no matter how big the chance is we will go for it. We need to recover from this disappointment and prepare for the next game."
A number of key Arsenal players have failed to live up to expectations at the Emirates, especially striker Olivier Giroud.
"I felt he [Olivier Giroud] had an off night tonight," Wenger explained.
"He missed easy chances and it looked like it was not one of his best days.
"He's [Alex Oxlade-Chamberlain is] very disappointed [for the mistake leading to Monaco's third goal] but it can happen that you lose the ball 70 metres from goal.
"It doesn't mean you have to concede a goal, you have defenders behind you."
