Upshaw, who led Oakland with seven sacks last season, suffered the injury on Thursday during light contact drills on the opening day of the Raiders' three-day mandatory mini-camp. Upshaw got tangled up and fell to the ground, twisting his knee in the process, though at the time it didn't appear to be a serious injury. After being checked by team trainers, Upshaw was helped to his feet and walked away with only a slight limp.
But a magnetic resonance imaging (MRI) test conducted Friday revealed that Upshaw had indeed torn the ACL in his knee. It's the same injury that knocked cornerback Eric Allen out for the year in 1998 and the same injury that forced center Barret Robbins to miss virtually the entire 2001 season.
''It was a weird-type injury because he had come up the field, made a spin move inside and off that move it looked like he had tweaked his knee,'' said Raiders head coach Bill Callahan. ''There's a little bit of collapse you can see on film, not to a great degree. Those things are weird. You get in a funny body position and you come of a move and you get caught with your cleat in the ground in a weird position and that knee just torques.''
Upshaw was at the team's facilities in Alameda on Saturday and sounded upbeat considering his situation. The 26-year-old Upshaw said he expects to have surgery on his knee next week before beginning what is expected to be a six-month recovery period.
''I'm on a rehab mission now,'' said Upshaw. ''I can basically charge this year to the game. It was a kick in the stomach for about 10 minutes then I looked at my situation and it was like, OK, what can I do here? What are my options? My only options are to rehab and I've got faith.
''I'm upbeat. I'm very upbeat. I've got God in my life. It's just another obstacle that I have to conquer in my life and I'm going to conquer it. I'm going to deal with it either with a good attitude or I'm going to deal with it with a pout attitude. My momma didn't raise me like that. It's not going to happen.''
The injury to Upshaw means the Raiders will be without three of the four starters from their defensive line in 2001. Defensive tackle Grady Jackson joined the New Orleans Saints in free agency while Darrell Russell is sitting out the season due to a one-year suspension by the NFL.
Callahan said that DeLawrence Grant, Emil Ekiyor, Chris Cooper and rookie Kenyon Coleman are possibilities to replace Upshaw in the starting lineup. Callahan ruled out using Trace Armstrong in an expanded role, preferring instead to use him primarily in passing situations.