This reminds me of a time when me and a few buddies were going camping and the morning before we leave my friend insists on doing some martial arts practice before he goes, well as it so happens he ended up tearing his ACL and couldn't walk for a good few months. We always ragged on him how if he had just listened and came camping right away he would of been fine, not sure if it really works that way though - could of been already messed up and was a ticking time bomb.
ANYWAYS,
it does seem like a pretty short rehab stint if hes up by Monday, his timing might be messed up.