DENVER -- Brian Griese's sprained left knee will keep him out of Denver's lineup against Indianapolis next weekend and could sideline him for three weeks.

Broncos coach Mike Shanahan said his quarterback will not practice this week after being injured in a 31-9 victory over Seattle on Sunday. Griese was hurt late in the third quarter when Seattle defensive tackle Rocky Bernard rolled into his knee.

The Broncos initially said Griese could be out up to a month, but lowered the estimate Monday after an MRI exam showed a second-degree sprain of the medial collateral ligament.

"It might be a little quicker than we first anticipated with three to four weeks,'' Shanahan said. "You never know for sure until he actually gets treatment and we see how he reacts to it. But Brian's tough. He'll get back as soon as he can.''

Shanahan said the good news was that Griese didn't have much swelling or a dramatic loss of motion that typically comes with such an injury. He said Griese's return will depend on how quickly the ligament stabilizes.

"I'm sure it's the stability of the knee,'' Shanahan said. "A lot of guys can play with pain, but when it's not stable and you can't make the cuts, you can't put too much pressure in that area.''

Steve Beuerlein, who threw two four-quarter touchdown passes in relief of Griese, will start against the Colts on Sunday night.

It will be the 37-year-old Beuerlein's first start since the final game of the 2000 season, when he played for Carolina. He missed last season with an elbow injury.

"I've been in this position so many times in my career I know how to handle it, I believe,'' said Beuerlein, who's in his 16th season. "I'll be very focused and very determined to go out there and keep an even keel. I'm going to go in there confident, poised and ready to execute whatever's asked of me, and hopefully do my job at a level that's acceptable to everybody.''

Shanahan nearly replaced Griese with Beuerlein in the third quarter of Denver's season-opener against St. Louis, but he said Monday there's little doubt who will start once Griese is healthy again.

"No questions asked -- unless Steve plays really well,'' Shanahan joked. "I just figured you'd have nothing to write about for a few days, so I thought I'd stir it up a little bit. Brian will get his job back.''