Arsenal captain Robin van Persie admits they struggled with QPR's energy for Saturday's derby defeat.

The Dutch ace put the slip-up down to QPR making it hard for them and Arsenal not seizing the momentum after Theo Walcott levelled in the first half.

Van Persie said: "It was a tough game. I always thought after Theo scored his goal and we were level we could win the game. It was just a tough game."