Ex-Arsenal goalkeeper Jens Lehmann admits that doubts over his former club's title chances are creeping in after a mixed start to the season.

Arsenal were beaten 2-1 by Dinamo Zagreb in the Champions League on Wednesday, having already opened their Premier League campaign with a defeat to West Ham.

Lehmann, who made 148 Premier League appearances during five seasons at Arsenal, gave his former club his full backing, but added to predictions that Arsene Wenger's squad might fall short again this year.

"I hope Arsenal will win the Premiership this year. Watching the game against Dinamo Zagreb, where they have lost again, there is always the same doubt," he told Omnisport.

"But the players said that this season is becoming a special season, and something special will happen. I hope that they are right, in a positive way."

Lehmann backed fellow goalkeeper Petr Cech, who Wenger rested in Zagreb, to become a key player in Arsenal's campaign, following his move from Chelsea.

The former Germany international said: "Petr is one of the greatest goalkeepers ever, so I think that was a really good purchase by Arsenal.

"You can't perform in every game, but Petr has the ability to tick every box in terms of goalkeeping. He doesn't really have weaknesses.

"He perfectly suits Arsenal, and hopefully will be one of the key factors to win something at the end of this season."

Arsenal's hopes of finishing in the Premier League's top four have been boosted by Chelsea's miserable start to the season, which has seen them take just four points from their first five games.

But Lehmann believes Chelsea manager Jose Mourinho will be out to prove his critics wrong – starting with Saturday's clash with Arsenal at Stamford Bridge.

"Now he probably wants to show people that, even with a bad start, he can become a champion, which would be special again," Lehmann said.

"But we will see. I doubt that, because they are already 11 or 12 points behind [Manchester City], so he needs to pull out something really special to get that right again.

"I don't know whether he is capable of doing that."