McClaren said: "As you'd expect, David is devastated. His absence is another big blow for us.
"David was one of them and, unfortunately, we're now going to be without him.
"His performances at the end of last season against Brazil and Estonia warranted him staying in the squad and getting another opportunity to prove himself.
"Going to America and playing for England was always going to be a difficult schedule for him but it was something he felt he could handle.
"But we're not going to be able to judge the evidence of that because he's injured and that's not necessarily because of all the travelling he has to do.
"He was unlucky to get a knock playing for us against Estonia and he never recovered sufficiently to play enough games to get his fitness back.
"I've talked to David and after these two games we'll assess his situation week by week, see how quickly he recovers and then decide if he's going to be available for the games in October."