Arsenal defender Per Mertesacker says the Gunners have to improve in attacking and defending set-pieces.
Arsene Wenger's men have been criticised in the past for failing to properly deal with aerial danger and the German believes it's an area where the Gunners still have to improve.
"We have to go through the set-pieces and say what went wrong because last year we had quite a good record," he told Arsenal Player.
"We need to improve on it this season because we've conceded from them already.
"It's all about reminding ourselves how good we are in the air from set-pieces, but we have to get to the ball and stop opponents getting into dangerous areas.
"That's what we need to improve. We had a good record throughout last season but we need to find that again quickly.
"[Attacking corners] is a part we have to improve as well. The deliveries, the timing, there's a lot of detailed things we have to improve.
"A lot of it has to do with concentration, strictness and good deliveries and good timing.
"When we went through the situation we could see that not everyone was on the ball.
"We have to be able to score or avoid conceding goals. We have to make sure that we are ready and concentrating on every set play."