By Chris Harris

Arsène Wenger admits his new-look defence needs time to develop into an effective unit.

Arsenal have been relatively watertight in Europe, conceding just twice in three Champions League matches. But they have leaked 14 goals in five Premier League fixtures, including 12 in their last two away games at Manchester United and Blackburn.

Wenger fielded two new signings in his back four at Ewood Park on Saturday - Per Mertesacker and Andre Santos - and Arsenal's defence looked vulnerable to the counter-attack, especially in the second half. The manager expects to see an improvement soon.

“I believe there is a little question of time and timing," he told Arsenal.com.

"Andre Santos and Per Mertesacker are new, but they were not especially guilty on the goals. But maybe as a unit we need more time to work.

“A lack of concentration, a lack of communication, a lack of coordination and individual urgency [is behind the goals we have conceded].

"When you score an own goal, you have to look at yourself. It is never completely out of your reach where you have no chance at all. All the rest, you have to look at yourself.”

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    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 19 Sep 2011