Are Arsenal serious title contenders?

Feted as serious title contenders after last season's FA Cup final rout of Aston Villa and their recent Community Shield victory over league champions Chelsea, Wenger's side came crashing down to earth on Sunday as West Ham clinched a shock 2-0 win at the Emirates Stadium.

A calamitous misjudgement from Petr Cech allowed Cheikhou Kouyate to net West Ham's opener and the Arsenal goalkeeper's slow reaction was also partially to blame when Mauro Zarate bagged the second goal after pouncing on a careless pass from Alex Oxlade-Chamberlain.

It was a familiar story for Arsenal, whose age-old inadequacies were on display as they failed to turn territorial dominance into goals, then found themselves outmuscled by more physical opponents who punished their defensive flaws.

Wenger admitted the result was a significant blow to Arsenal's pre-season optimism, but he called on them to bounce back at Crystal Palace next Sunday and avoid a repeat of last season's slow start.

"It is difficult (to recover) but it is part of our job," Wenger said.

"In any successful team it is how you respond to setbacks that matters.

"It is never a clear motorway. We have to respond quickly because we have a difficult start. Crystal Palace are a good team."

Cech's dismal debut was especially galling after he was hailed as the solution to Arsenal's long-standing goalkeeping problems.

Instead, Wenger must have felt a depressing sense of deja vu as he trod a delicate line between backing his keeper and making clear his unhappiness at such a costly mistake.

"When you concede the goal before half-time, with the experience in our team, it was difficult to understand," he said.

"It is not only him (Cech), we have enough experience at the back. We are guilty to give them a goal as soft as that, but it was a collective lapse.

"There are many things to say about that. I knew we were in trouble even before the free-kick was taken.

"I can't see many convincing individual performances. It's difficult to see beyond that."

- Lacklustre efforts -

Cech has been Wenger's only major signing since the end of last season and, earlier in the week, he was keen to distance himself from links with Real Madrid striker Karim Benzema.

Asked if he had changed his mind after the lacklustre efforts of France forward Olivier Giroud against West Ham, Wenger said: "If an exceptional solution turns up we do it, but it's important not to think we must take a solution from outside."

While Arsenal struggle to come to terms with a catastrophic start, new West Ham manager Slaven Bilic revelled in a result he hopes will convince his players to trust his methods.

Criticised for fielding a weakened team when West Ham bowed out of the Europa League in midweek, Bilic's decision to keep his senior stars fresh was rewarded with his club's first win over their London rivals for eight years.

"It's really a great start," he said. "The players will always say they believe in you and your tactics, but the best thing is when you have a great result like this. Then they know it works."

One of the keys to West Ham's victory was the remarkably mature Premier League debut of 16-year-old Reece Oxford, who shone in a midfield holding role just weeks after the Londoner became the club's youngster ever player.

"He did a great job. He has a presence, he is a very cool guy, he was not fazed or impressed by playing at the Emirates," Bilic said.

"He is still 16, just a boy, but he is definitely going to be a big player.

"We have to manage him off the pitch as well to make sure he can progress."