A league source, however, told ESPN NFL Insider Adam Schefter the Bears fear that Urlacher tore both his MCL and PCL. Urlacher will undergo an MRI to see if the initial diagnosis is correct, the source said.
Urlacher and Bears safety Major Wright leaped in the end zone to break up a pass to the Vikings' Percy Harvin and Urlacher landed awkwardly on his left leg. He fell to the ground and took his helmet off in pain as medical staff came out to examine him.
"I just went up for the ball," Wright said. "We all went up for the ball, and I kind of reached over him a little bit and my weight landed on him."
Urlacher was able to walk off the field under his own power with a noticeable limp. Once on the sidelines, the Bears medical staff wrapped Urlacher's left knee in ice and eventually took him to the locker room.
The 33-year-old Urlacher, who was voted to his eighth Pro Bowl, missed two straight days of practice this week before returning on Friday.
"All we can do right is just sit back and pray. I hope he's OK," Wright said.
Jeff Dickerson covers the Bears for ESPNChicago.com and ESPN 1000.