Ex-Arsenal goalkeeper Jens Lehmann has warned Petr Cech that he must take advantage of his opportunity to impress Unai Emery.

The Gunners manager elected to use Cech in Sunday's loss to Manchester City, ahead of Bernd Leno, who arrived from Bayer Leverkusen for £19.3m this summer.

And Lehmann believes Cech must be wary of his rival for the number one spot.

"There's a new guy that came in for £20million," he said. "He's competition.

"We don't know who the coaches like. If he tries a new player out, if not the other guy is playing.

"Bernd is a good 'keeper, no doubt about that. The question is: can he show more than he did in the past?

"He must take more risks and continue his development. He does that - good!"