Wenger fielded a much-changed side with top spot in Group F already sewn up and his fringe players failed to rise to the occasion.

"We must give credit to Olympiacos tonight because they played a very physical game and in the first half it was very difficult for us," the Frenchman said on Sky Sports 2.

"And I don't think we had the right tactical approach.

"In the second half at 2-1 we looked like we might come back, but they were dangerous and probably deserved it.

"Many of the players did not have experience in the Champions League so were a bit surprised by pace of game."

Arsenal lost goalkeeper Lukasz Fabianski to injury in the first half and replacement Vito Mannone was at fault for the goal he conceded shortly after coming on.

But Wenger had words of support for his keepers.

"I think we didn't help our goalkeepers," he said. "We exposed them with our lack of quality in the passes we gave them and they were quite brave."