Torn ACL means 6 months until you play again now thanks to pioneers like Dr. Andrews. I am good friends with a college player that tore his in March and was running full speed by June and participating in most drills. Using a cadaver donor ligament, guys are up and walking in days and not even wearing a brace for normal movement within weeks. It's not what it used to be. ACL's are very common, and for some people, getting it fixed actually improves the health of a knee that has been beaten up for years. A lot of guys are playing on partial tears, and the replacement actually helps in some regard because the injury itself doesn't cause pain. The new ligament leads to some strength they didn't have prior to the injury. Sounds crazy, but is true.
I had a ligament removed entirely from my ankle because it was shredded entirely. They did microfracture in the area as well and I was up and around in five days and playing sports again in 6 weeks. It is amazing what they can do now. If a nobody like me can play sports again, then I know a physical specimen like Chris Clemons will come back hungry and play well. He's at about the same point in his career Kerney was, and Patrick suffered a "career ender" and then came out and nearly won the defensive player of the year for the Hawks. Don't count Clem out.