I am not a doctor so I don't know how bad the Patellar Tendon injury is compared to an ACL, but here is a story that claims it is worse:
That Carnell Williams Knee Injury?
Bad. Not your now run-of-the-mill ACL issue. But the far more serious patellar tendon one. The one Cleveland's LaCharles Bentley still has not made it back from (his injury was the start of camp 2006). And the quotes from the doctors are less than optimistic:
"'That injury at the running back position is a tough one to come back 100-percent from,' said Dr. Johnny Benjamin, chairman of orthopedics at Indian River Medical Center of Vero Beach. 'Leg strength and drive are very important [and] hard to generate after this type of injury.'"
http://www.sportsfrog.com/2007/10/that_car...ms_knee_inj.php
A contrary opinion:
CBSSports.com spoke with former Bucs and current Rams assistant head coach/running backs coach Art Valero, who is familiar with Cadillac Williams' knee injury and rehab. "From what I hear from teammates and trainers in Tampa Bay, he is making great strides," Valero said. "I know that kid, and I know that young man has so much unfinished business ahead of him, he's going to be like so many other running backs that won't take no for an answer. He is driven, and great things will happen to him. I texted him the other day and wrote that another great running back who came back from knee surgery was Gale Sayers, and that he can do what Sayers did. He's got so much that he wants to continue to do with this game that there's no way. He'll be back, I guarantee it."
(Updated 03/13/2008).
http://sportsline.com/nfl/players/playerpage/423701