I'd be more inclined to think along those lines than the other scenarios being touted. Apparently he felt a twinge in the first 5 minutes of the last game according to the commentary. He went on to play the full 90 without any problems whatsoever and looked at ease throughout.Perhaps its an attempt by the Belgium team manager to build bridges with City following the recent fall out. A gesture on their part rather than a serious injury.
Going away on international duty, especially for meaningless friendlies was the perfect opportunity to rest. He was never going to pull out, anyone who's been paying attention to his love of his country will tell you that.
I'm willing to wait and see what happens before selling him off.