It is sometimes helpful to wait a bit after the injury to let the trauma and swelling go down before surgery. Assuming there are not extensive injuries to other parts of the knee, you can live without an ACL and even do some straight ahead exercises like biking. So, if he they are patient enough to wait for surgery, AM may benefit in outcome because his injury occurred before the beginning of the season. I am not suggesting he wait this long, but I had ACL replacement a few years after injuring it, and 30+ years later with a very active lifestyle, I am lucky to have absolutely no residual impacts from the injury.