Theo Walcott was not called to play in this summer's European Championship. Michael Regan/Getty Images

Thierry Henry believes Theo Walcott's exclusion from the England squad while Alex Oxlade-Chamberlain and Danny Welbeck are injured proves how much he has disappointed.

Walcott spent 18 months playing alongside Henry at Arsenal until the Frenchman's transfer to Barcelona, having been described by some as his successor when joining the Gunners in 2006.

A surprise call-up to England's World Cup squad that summer further increased the forward's profile, but he has since appeared at only Euro 2012 after a poor season again led to him being overlooked.

Henry believes the uncertainty over Walcott's best position -- whether to use him out wide or in a central role -- is part of the problem.

"He has struggled,'' said Henry.

"His 10 years at Arsenal have been a weird one. Apart from one season where he played more than 30 games, he wasn't really a starter. If Welbeck is out and Oxlade-Chamberlain is out, we all know how important pace is in the way [England manager Roy] Hodgson wants to play.

"If you go, you have to have performed.

"I always have a mixed reaction, Theo Walcott has been in the game for 10 years, you should know about him. You always have something to prove, he should know what he can offer to a team.

"By now he should know what his position is, but it is not clear.''

The inclusion in Hodgson's squad of another Arsenal player, Jack Wilshere, has similarly divided opinion over concerns about a lack of fitness after he missed almost the entire season with a broken leg.

Henry believes the midfielder's talent is such that his place at Euro 2016 is justified, however, but remains concerned a lack of match-sharpness could undermine him.

"It was a case of him getting back to a certain fitness so that he can go, based on his talent I don't think there is a question,'' said the BBC pundit.

"When a guy is special he is treated in a special way.

"He needs to have some match fitness. It is one thing to go but can you play? If you go and you can't perform, well that is another thing.

"You can train for eight months and think you are fit but once you play that first game, you sometimes need a month to get back to that level.''