GREELEY, Colo. (AP) Injury-plagued running back Terrell Davis had an MRI exam on his swollen left knee Sunday after he missed the Denver Broncos' preseason opener the day before.

Results were not expected until Monday, and coach Mike Shanahan said he didn't know the severity of the injury.

"I have to talk to the doctors," Shanahan said. "I've got find out where the knee is, what they think, what happened, why his leg was sore, why he couldn't go, take a look at the MRI. I've got to get a number of questions answered before I can answer you guys."

Davis, who's struggled with knee injuries the past three seasons, was scheduled to start against Chicago on Saturday, but pulled himself out just before the game because of swelling in the knee. He also had the knee drained of fluid earlier in the week.

"What I'm saying is, I don't know," Davis said after the game. "I'm taking a wait and see attitude at this time. I feel pretty upbeat. I don't like having setbacks like this. It tends to throw me off track."

Davis, the league's MVP in 1998 after rushing for 2,008 yards, tore the anterior cruciate ligament in his right knee in the fourth game of the 1999 season.

He played just four games the next year with left foot and ankle injuries, and played just eight last season after having arthroscopic surgery on both knees.

Davis had surgery to remove loose cartilage fibers and scar tissue from under his left kneecap in May, but was back on the field for a minicamp three weeks later. He had been practicing just once a day during training camp, but was running hard and seemed to be pain free.

"The weird thing about it is that it's supposed to be my pristine knee, the knee that didn't really have any problems," Davis said. "I really don't know. I'm sitting over there like, `what's going on?' I guess we'll see what direction we're going to head in."

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