Fabianski was substituted just before the half hour mark, following a nasty collision with team-mate Thomas Vermaelen, but the Polish keeper believes it was clear from the start that Olympiakos were keen to secure the three points.
He told Arsenal’s official website: “I can only talk about the time I was on pitch because afterwards I didn't see anything.
“You could see that Olympiakos were really up for it and they were pushing hard. The first goal we conceded was a bit unlucky because it went off our defender.
“We could have maybe come back in a different way but unfortunately we didn't and that's how it finished.”
The 26-year-old also remained upbeat about the injury he sustained during the game, and is hopeful of a return to action sooner rather than later.
“I think I am fine, it's just a really deep cut,” he added.
“It was really unlucky but hopefully all the ligaments in my knee should be OK. Hopefully nothing will come out tomorrow or in the next couple of days.”
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