Arsenal manager Arsene Wenger bristled over suggestions he was wrong to pick David Ospina over Petr Cech in Tuesday's Champions League defeat to Olympiacos - adding that "no goalkeeper is mistake-free".
Ospina fumbled a corner over his own line to give Olympiacos a half-time lead after Theo Walcott had cancelled out Felipe Pardo's opener at the Emirates Stadium.
Alexis Sanchez gave the home side hope but Alfred Finnbogason struck soon after to condemn Arsenal to back-to-back Champions League defeats, denting their prospects of qualification from the group.
When quizzed about the decision to leave out number one Cech, Wenger responded: "I do not have to sit here and give you an explanation about every decision I make.
"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."
Wenger saw Laurent Koscielny limp off with a hamstring problem midway through the second half on a difficult night for Wenger and his side.
When asked whether he had any regrets, he added: "Honestly, I don't want to go into that conversation with you.
"It leaves us in a bad position but we are still in it. We have to get a result in our next game against Bayern at home.
"Some aspects of our game were quite good but we lacked quality in our defensive concentration. I believe we had a bit of bad luck as well - they had four shots on target and scored three goals.
"The turning point was at 2-2. We got back in the game and then gave them 3-2 straight away. Tonight we feel guilty because we gave easy goals away."
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