By Chris Harris

Arsène Wenger acknowledges that defending set-pieces has been Arsenal's Achilles heel this season.

By the Frenchman's reckoning his team has conceded fewer goals from open play than any of their Premier League rivals but more than 50 per cent of the 39 shipped in the top flight have come from corners or free kicks.

Arsenal looked vulnerable in those situations during last weekend's 3-1 defeat at Stoke and they fell behind when a delivery from near the corner flag was allowed to reach Kenwyne Jones.

"It has been [a problem]," admitted Wenger. "We cannot deny that because we conceded more goals from set-pieces than other teams. But you have to consider as well that we conceded 17 penalties."

With Thomas Vermaelen expected to return to the first team on Sunday, Wenger was asked whether the Belgian centre back could have helped Arsenal address their weakness from dead balls.

"I feel certainly a little bit, but I feel it is more about the size of our whole team in some games like Stoke," he replied.

"When you go out of the back three, after that we are quite short, especially when Abou Diaby wasn't there for big games. When you have the defence plus Diaby and Alex Song, and you go to places like that, you can of course fight.

"Sometimes we're one or two men short."

Copyright 2014 The Arsenal Football Club plc. Permission to use quotations from this article is granted subject to appropriate credit being given to www.arsenal.com as the source 13 May 2011