Arsène Wenger says Theo Walcott’s bad luck when it comes to World Cups is “unbelievable”.

The Arsenal forward has been ruled out of this summer’s tournament is Brazil after rupturing the anterior cruciate ligament in his left knee.

Walcott was controversially left out of the England squad for South Africa 2010, and was an unused squad member as a teenager in 2006.

We know deep studies show that the players of around 25 with that kind of injury come back as normal

Arsène Wenger

“He went to the World Cup when he was certainly not ready and then, when he was ready to go, he was not selected,” Wenger said. “This time, when nobody disputes that he will go, he is out through injury. It is unbelievable.

“He is strong mentally and if you look at his career, he has had a few setbacks, a few disappointments. He has had a few things to handle that are not easy to handle.

“To go, at 17 years of age, to a World Cup and after that to be left out in South Africa was certainly a massive blow to him.

“He always recovered from it in a very strong way so I’m confident he will do so again. What he has said to me is that he is in shock but he will fight to come back.”

Wenger also believes that time is on Walcott’s side as he prepares to start his recovery.

“We know deep studies show that the players of around 25 with that kind of injury come back as normal,” he said. “When you’re over 29 or 30 you do not ever come back exactly the same. But between 25 and 28 you come back to the level you had before.”

Copyright 2014 The Arsenal Football Club plc. Permission to use quotations from this article is granted subject to appropriate credit being given to www.arsenal.com as the source Rob Kelly 10 Jan 2014