Shearer wrote in The Sun: "Walcott wants to play down the middle and his goal return this season has been good, so he is pressing his case.
"He is able to play down the middle and out wide, and that versatility may be to his detriment.
"If he doesn't specialise, it will be hard for him to be GREAT. Unless you play in a position regularly, you cannot master it.
"Don't get me wrong, I think Theo is very good. After years of people speaking about his potential, this season we have seen him fulfil it more than ever before.
"But is he ever going to be the No 1 centre-forward at Arsenal?
"You have to have your doubts."