Arsenal defender Per Mertesacker has said that his side weren't switched on at the back after Arsenal lost the North London derby to Tottenham Hotspur.

Mesut Ozil had put the Gunners ahead, but a second-half brace from Harry Kane won the game for Spurs, and Mertesacker has admitted that the defence wasn't prepared.

He told Arsenal TV: "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.

"We were not active enough and only started to play our game a bit towards the end, that took us too long. 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.'

Arsenal sit sixth in the Premier League table.