"Michael has not played a game for us yet this summer because he had a slight calf problem," Toon boss Kevin Keegan told the club's official website.
"I will clear it up - it's not mumps. He missed the England games earlier in the summer because of mumps but for us it's been a slight calf.
"He's back training and has passed injury but he's got to get match fit.
"Even if he had come over here he would not have played."