The Gunners have taken just seven points from their opening six league games, suffering defeats to Blackburn, Liverpool and a humiliating 8-2 mauling at Manchester United.
And Wenger believes having to qualify for the Champions League via the playoffs and then facing a difficult trip to Germany has adversely affected his side.
"We've paid a heavy price in the Premier League for the quality of our performances in the Champions League," Wenger told reporters.
"The Udinese away game was terrible for us because it was 33 degrees and we had to give everything. We lost three or four players in that game and then we had to go to Man United. It was a bit too much.
"After we went to Dortmund, we went to Blackburn and so we've had the bad luck to play twice away after the Champions League, and it's difficult for everybody.
“Look on Saturday at what happened [when Arsenal beat Bolton Wanderers, having not played in the Champions League in midweek]."
Wenger is without several key men ahead of their Champions League tie with Olympiakos. Thomas Vermaelen, Laurent Koscielny, Johan Djourou and Sebastien Squillaci are all sidelined with injury problems, meaning Alex Song will have to play at centre-back.
Meanwhile, further up the pitch Wenger has similar woes, with Theo Walcott, Gervinho, Abou Diaby, and Yossi Benayoun all out injured.
Wenger hopes to welcome back Koscielny, Walcott and Gervinho for Sunday’s game at rivals Tottenham, while Djourou, Squallaci, Benayoun, Vermaelen and Diaby are just a few weeks away from fitness.
Jack Wilshere, however, appears to be a more long-term casualty. The England man has undergone surgery on his ankle after the club’s medical staff found a crack in his bone. Despite predictions of him being sidelined for around five months, Wenger is remaining positive about the situation.
He continued: "When people go into surgery, you never know what they will find.
"What they found was a very clean ankle and they came out very positive. They said that it was better than they expected it to be.
"People say to me that the crack didn't heal because there is no blood supply so it doesn't glue together any more. When you see the scan, it looks like a little hole in the bone.
“We needed to screw that together because it wouldn't heal. When he was in the boot, it did not get better. It can be [that it got] even worse."