“That is the big regret. We started the second half on the front foot, but at times it was too much and that was a bit naïve,” said Mertesacker.
“When you're 2-1 down, you think you can maybe score another one, that is what we thought. We were really up for the second one.”
Arsenal have it all to do in the second leg, needing a big performance from the team to overturn the odds and progress to the next round.
It was a surprising defensive performance from Arsenal because of the superb display they put in against Manchester City away from home in a 2-0 win.
For them to beat Monaco away from home, the defence has to be much more resilient while the attack has to be clinical and precise with their finishing.
There is confidence to be drawn from previous away performances in the Champions League, with positive results in recent seasons for Arsenal away at Bayern Munich and Borussia Dortmund.
It’s possible but they need a lot to go in their favour and for Monaco to produce an even worse defensive display than the Gunners managed themselves last night.
The focus now switches to reacting in the right manner for the side against Everton this weekend.