Arsenal legend Liam Brady has told manager Arsene Wenger that he must work on the team's defence following their Champions League defeat to Olympiacos.

The Gunners are bottom of Group F after losing 3-2 to the Greek side at the Emirates Stadium on Tuesday evening, having also lost their opening game in the tournament to Dinamo Zagreb a fortnight ago.

With Theo Walcott and Alexis Sanchez both scoring against Olympiacos, Brady has said that it is the defensive side of Arsenal's game that needs improvement.

"We don't have a problem in the forward area, not as much as people like to make out," Brady told talkSPORT. "Theo will play. He scored again last night and did really well for Sanchez's goal.

"It think our defending, especially in set pieces, is where we really need to get better. We dominated the game, but we defended poorly from set pieces and it cost us dearly. We lost a goal at Zagreb and two goals against Olympiacos to set pieces.

"The first goal was bad last night, the ball coming into the box and players not really knowing what's going on. The marking and concentration has got to be a lot better. If we get these things right the results will be more consistent and we won't have this up and down situation we're having at the moment."

Arsenal face Manchester United in the Premier League on Sunday.