Arsenal boss Arsene Wenger says they will need to take three points away from home if they are to qualify for the last-16 of the Champions League.

They are still top of Group F but only on goal difference after a 2 - 1 home defeat by last season's runners-up Borussia Dortmund at the Emirates.

Robert Lewandowski's late goal came against the run of play with the Gunners pushing for a winner.

Wenger said a lack of concentration on Arsenal's part, cost them at least a point:

Arsenal, Dortmund and Napoli all sit on six points in the group with the top two progressing to the knockout stages.