Just as you thought, rehab and recovery after an anterior cruciate ligament (ACL) repair to the knee will keep your son on the bench this season. Even prime athletes need four to six months to fully recover from this operation. Many athletes are out a full year, but they can come back to competitive play.
In the case of wrestling, your son may have to work to get back all the moves he needs. It depends on the type of surgery he has to repair the torn ligament. For example there
are some leg positions needed to control the opponent. Leg locks and hooking action needed for these maneuvers may be weaker after surgery and rehab than before. This is especially true when a graft from the hamstring tendon is used to replace the torn ligament.
When your son has his doctor's approval to return to wrestling, the coaching staff will help him develop some alternate positions and options until he gets his full motion and strength back.