Defender Per Mertesacker admits Arsenal's defensive department should have done better to prevent striker Harry Kane from scoring two goals in the North London derby.
The Gunners took an early lead through Mesut Ozil but struggled to cope with the constant pressure coming from Mauricio Pochettino's men and when they did react, the German says it was too late to recover.
"We were not active enough and only started to play our game a bit towards the end, that took us too long," Mertesacker told Sky Sport.
"We found a way recently to prepare ourselves on crosses better defensively [and also] on set-pieces, but we did not switch on quickly enough and were not up for proper defending, so that was worse than in recent weeks.
"When we had the ball, we could not find any solutions, they were always at us and we could not get the ball quickly in our own half so we could not hurt them on the counter-attack.
"We have to analyse the problems they caused us, then we focus on Tuesday to bounce back from this setback as quickly as possible."
