Arsene Wenger says Jack Wilshere is downbeat following a fracture to his left fibula but backed the Arsenal midfielder not to lose a combative edge on his return.

The England international sustained the injury in training and is expected to miss around a month - Wilshere continuing to be plagued by injuries ahead of the new Premier League season.

The 23-year-old missed five months of the 2014-15 campaign with ankle ligament damage but returned to help Arsenal defend the FA Cup in May.

"There is minimal damage apart from the bone damage - there is no damage at all apart from that. It was a collision in training and it was all completely accidental," Wenger explained.

"He's down but he's coping with it. He'll play with the same confidence and desire when he comes back.

"You never get used to that, you never get used to your body letting you down.

"The positive thing is that it's not a recurrence of an old injury and also another positive is that the history of his injuries doesn't play a big part in his head.

"He plays with the same confidence and desire. It's difficult when you are at that age - when you love to play football but can't it's mentally difficult."

Arsenal get their league campaign under way against West Ham on Sunday before travelling to Crystal Palace the following weekend, with Alexis Sanchez potentially returning for the latter fixture after his Copa America exertions.

"We're ready for a fight and we're motivated to start well. One of our targets is to start strong," Wenger added.

"We have the needed ingredients to succeed but we have a tricky start with two London derbies."