There were a lot of things wrong with the Arsenal performance on Tuesday night, but David Ospina was the obvious one.

The Colombian goalkeeper was unassured and incompetent as Olympiacos snatched a shock win at the Emirates Stadium in the Champions League.

The Greek champions won 3-2, but it was the goal that put them 2-1 up that will grab most of the headlines. A corner seemed to be swinging into Ospina’s arms fairly comfortably, but the goalkeeper failed to catch the ball and it ended up crossing the line.

Arsenal's Colombian goalkeeper David Ospina (C) drops the ball over the line from a corner taken by Olympiakos's Greek midfielder Kostas Fortounis for Olympiakos's second goal credited to Fortounis during the UEFA Champions League Group F football match between Arsenal and Olympiakos at The Emirates Stadium in north London on September 29, 2015. AFP PHOTO / GLYN KIRK (GLYN KIRK/AFP/Getty Images)
Arsenal’s Colombian goalkeeper David Ospina (C) drops the ball over the line from a corner taken by Olympiakos’s Greek midfielder Kostas Fortounis for Olympiakos’s second goal credited to Fortounis during the UEFA Champions League Group F football match between Arsenal and Olympiakos at The Emirates Stadium in north London on September 29, 2015. (GLYN KIRK/AFP/Getty Images)

The decision to play him over Petr Čech was questioned before the game, but Arsène Wenger defended the choice when he faced the media after the match.

“That is a simple thing. David Ospina played 19 games last season and kept 14 clean sheets,” said the Arsenal boss. “Last week he had a fantastic game. No keeper is mistake free, it could have happened to Petr Cech as well.”

But it didn’t happen to Petr Čech, it happened to Ospina. As fans the manager doesn’t have to tell us anything, but he does perhaps owe it to us to explain his decisions – particularly when they go wrong.

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Many fans have questioned Ospina and will once again be calling for his head after Tuesday night.

Hopefully Petr Čech will be back in goal for Sunday’s visit of Manchester United.