London: Per Mertesacker accepted Arsenal undid all of their recent good defensive work by not being "switched on" in allowing Tottenham to come from behind to win the north London derby 2-1 at White Hart Lane.
"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," Mertesacker said on Arsenal Player.
"We were not active enough and only started to play our game a bit towards the end, that took us too long."
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