The 22-year old Gunners midfielder started in England's 1-0 friendly win over Denmark on Wednesday night before being replaced by Southampton's Adam Lallana prior to the hour-mark after he sustained a foot injury.
It has since been revealed that Wilshere sustained a hairline fracture in his left foot but regardless of the problem, former Leeds United and Manchester City man Mills feels he is not quite up to international standard ahead of the 2014 World Cup.
"I'm not sure Jack Wilshere would make my squad. He seems to run like he's got a limp. I'm not convinced he's 90% fit, let alone 100% fit, but in a World Cup year players will push their bodies to the limit," he told Sky Sports News Radio.
"He might need an operation, he might need a rest, but he knows he has the chance to go to a World Cup and therefore might be trying to play through the pain barrier when he's not quite right. You cannot do that at the highest level."
Mills added: "The big concern for England is what happens if you lose Steven Gerrard to injury? You take his passing ability and his discipline to sit in front of the back four, there is not a single player that can fill his shoes.
"Wilshere's not strong enough (for that role). Physically he's not strong enough. He doesn't have that burst of pace to go past people.
"He is a continuity player, he passes it backwards, he's neat, he's tidy. How many goals has he scored this year, how many chances has he created?
"I know he's been involved in a couple of wonder goals but does he do enough week-in, week-out to say he has really lived up to his potential?"
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