http://www.natchezdemocrat.com/news/2009/aug/04/lsus-ridley-eager-return-field-after-nursing-acl/ Just a little tidbit, its a well written article, I know someone was asking about how he was doing.
Many who suffer torn ACLs especially young athletes can recover in that time. Even if you are older and/or not in shape, most can start walking and even running between 2-4 months after surgery. Either way I expect the staff to bring him along slow and I don't expect to see him in a game into the 1st month of the season.