Wilshere faces six weeks on the sidelines after suffering a hairline fracture in his left foot during England's friendly with Denmark on Wednesday night but, even before that news broke, Mills questioned whether Roy Hodgson should include the 22-year-old in his squad for the World Cup this summer.
Speaking before news of Wilshere's lay-off broke, Mills told Sky Sports News Radio: "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 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."
Even if Wilshere were fully fit, Mills has doubts over the midfielder and believes an injury to Steven Gerrard would represent a disaster for England.
He 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?"
To hear who else Mills would pick and leave out of his England team, listen to his full interview with Sky Sports News Radio via the Souncloud player below.