Gallery: Ospina's calamitous error contributes to uphill battle for Arsenal

Arsenal are left with a mountain to climb after losing both of their opening two Champions League group games.

Arsenal are facing an embarrassing early exit at the Champions League group stages after losing their two opening group games.

After their shock defeat to Dinamo Zagreb, a home fixture against Olympiakos would have been an ideal time to bounce back. They are opponents who the Gunners have faced numerous times in the competition down the years but the result wasn't the same.

A deflected effort by Felipe Pardo gave the visitors the lead but Arsenal hit back almost instantly through Theo Walcott. However, the home side went into half-time behind after David Ospina inexplicably carried a Kostas Fortounis effort over his own line. 

Alexis Sanchez restored parity midway through the second half, but they weren't level for long again as the Greek side regained the lead through Alfred Finnbogason soon after.

There are inevitably questions over Arsene Wenger's team selection, mainly why he left out first choice goalkeeper Petr Cech in order to give Ospina another game, especially given his costly error.

With two games gone in the group, Arsenal are bottom with no points and face Bayern Munich in their next two group games in the knowledge that they need to win at least one of them in order to have a realistic chance of progressing to the knock-out stage of the competition. It is by no means impossible but they could have done with going into those games without such pressure on their shoulders.

Here is a selection of the best images from last night's action: 

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