Arsenal manager Arsene Wenger found it "difficult to understand" how his side conceded a poor opening goal against West Ham.
Arsene Wenger refused to lay the blame for a surprise 2-0 Premier League defeat to London rivals West Ham solely with Petr Cech.
Big things are expected from Cech after he left Chelsea to join Arsenal just over a month ago, but the Czech Republic goalkeeper had a Premier League debut to forget for his new club on Sunday at the Emirates Stadium.
Cech flapped at a Dimitri Payet free-kick just before half-time to allow West Ham midfielder Cheikhou Kouyate to nip in front of him and head into an empty net.
A wrong-footed Cech was then beaten by a long-range Mauro Zarate strike at his near post 12 minutes into the second half and Arsenal were unable to summon a response, as they suffered a first defeat to West Ham in eight years.
Wenger was left to rue conceding two goals that were very much avoidable, but refused to single out Cech for criticism.
"I haven't spoken to him [Cech] yet, but I can't see many convincing individual performances. It is difficult to single one out," said the Frenchman.
"It's not only him, if you look at the back line we have plenty of experience at the back. I think the youngest is 30.
"We were punished for our defending. We gave two very cheap goals away and gave ourselves a mountain to climb.
"The way we conceded a goal just before half-time with the experience we have in our team is difficult to understand."
Wenger felt West Ham's participation in the UEFA Europa League - a tournament they were knocked out of on Thursday - worked in their favour and urged his side to show a positive response to a poor start to their Premier League campaign.
"West Ham are a bit more advanced in their preparation. They've played more competitive games than us and we knew that," Wenger added.
"We were a bit nervous and we didn't respect the basics. There were no individually convincing performances.
"A successful season is how we respond to disappointment. We have to respond quickly because we have a tricky start. We play Crystal Palace, a very good team, we play Liverpool, a very good team. You could see fitness-wise, physically we are not there yet."