Arsenal manager Arsene Wenger has refused to explain why he selected goalkeeper David Ospina over first-choice stopper Petr Cech for his side's 3-2 defeat to Olympiacos in the Champions League.

The Colombian was at fault for the Greek side's second goal, but the Gunners boss insists that he does not have to justify his team selection.

"I do not have to sit here and give you an explanation about every decision I make," he told reporters.

"That is always the simple thing. Ospina kept 14 clean sheets in 19 games last season and was fantastic against Tottenham last week. No goalkeeper is mistake-free.

"I make the decisions and selections for the team and I am responsible. I know many things that you don't know or you ignore. You can't select a team by taking a poll before the game and taking everyone's opinion."

The result leaves Arsenal rooted to the foot of Group F with two defeats out of two so far.