Arsenal suffered a shock 3-2 home defeat to Olympiakos in their Champions League Group F encounter. Gunners boss, Arsene Wenger, made five changes to the side that had won 5-2 at Leicester on Saturday, the most significant of which was in goal, with David Ospina replacing Petr Cech. It was a decision that Wenger refused to speak about afterwards, but one he must surely now be regretting, after the Mexican stopper made a horrible mistake five minutes before half time, dropping Kostas Fortounis's corner into his own net. That came just five minutes after Theo Walcott had cancelled out Felipe Pardo’s opener. Alexis Sanchez again levelled things for the hosts, nodding in on 65 minutes, but Arsenal’s defensive frailties were on show again, as Alfred Finnbogason immediately restored the Greek side’s advantage from the kick-off. It leaves Arsenal with the challenge of becoming the first team in three years to reach the knockout stages after losing their opening two games. That task is made harder by the fact that their next opponents are Bayern Munich, who romped to a 5-0 win over Dinamo Zagreb, with Robert Lewandowski again grabbing the headlines. The striker made history a week ago by scoring five goals in nine minutes, and though he didn’t leave the Allianz Arena with any records last night, he did have possession of the match-ball after scoring a hat-trick. Douglas Costa and Mario Gotze scored the other goals for the German champions.