Per Mertesacker believes Arsenal need to rediscover their killer instinct after they crashed out of the FA Cup on Sunday.

"It is as you can imagine, we are out of the competition and the treble dream is over, that is the conclusion of Sunday's game," said Mertesacker.

"The season is not over. We play in a confident way, we maybe lack that bit at the end. What is really important in football, to be successful we need to score. The desire to play together and to be good at a team is there, you can feel that, even if there is a bit of negativity I can understand."

"It looks like we play, and play and play until the opposing team scores," the Gunners skipper added. "That is something we need to work on. We had the opportunities and the possibilities when they were 2-0 up to come back and we kept going.

"You have to give credit because we kept going and created chance after chance, but at the moment we lack that killer instinct. We need to work on that if we want to be successful in the Premier League and the Champions League."