The initial diagnosis was that Vikings quarterback Tarvaris Jackson sustained a bruised right knee in Saturday's preseason game at Baltimore, but further tests revealed a sprain to his MCL, according to a person with knowledge of the situation.

Vikings coach Brad Childress was not available for comment yesterday, but it's reasonable to think the injury could keep Jackson out of the most important game of the preseason Saturday against the Steelers.

Teams typically treat their third preseason game as a dress rehearsal for the regular season, giving starters extended playing time. Jackson's status for the preseason finale at Dallas Aug. 28 also is unknown, but it's hard to imagine he would not be ready to play in the season opener Sept. 8 at Green Bay.

Jackson suffered the injury while scrambling in the first quarter of a 23-15 victory against the Ravens. Rather than slide to avoid contact, Jackson took on a hit by Ravens linebacker Ray Lewis and then safety Dawan Landry.

Asked if Jackson could have returned to Saturday's game had it been the regular season, Childress said: "He played for how many plays after that? So, chances are he could have. You still want to always be able to protect yourself so that's always kind of the litmus for us."

St. Louis offensive guard Mark Setterstrom fractured his left kneecap in the second half of Saturday's preseason game and will be placed on injured reserve.

Coach Scott Linehan said that Setterstrom, a seventh-round pick in 2006 who has made nine starts in two seasons, would have surgery later in the week.

Quarterback Marc Bulger, who hurt his shoulder when he was hit from behind while preparing to throw in the second quarter, was believed to be fine. Linehan said team doctors were not concerned.

"We'll just see how he feels throwing tomorrow, if he can," Linehan said. "From my standpoint I think he's going to be just fine."

Another offensive lineman, Brandon Gorin, also will be placed on injured reserve with a shoulder injury sustained in the preseason opener at Tennessee. Gorin made eight starts at tackle and played in 11 games last year.

Cincinnati receiver Chad Johnson landed awkwardly while trying to make a catch in the first quarter against Detroit, then left the game to have his left shoulder treated.

Cornerback Brian Kelly hit Johnson as he tried to pull in a pass from Carson Palmer on the Bengals' first series, jarring the ball loose. Kelly came up with the interception and an off-balance Johnson landed on his left side.

The Pro Bowl receiver rolled around on the field for several seconds, then got up and went to the sideline. Trainers examined the shoulder on the field before Johnson went to the locker room.

The Bengals already were without receiver T.J. Houshmandzadeh, missing his second preseason game with a sore hamstring.

Tennessee rookie receiver Lavelle Hawkins is wearing a walking boot on his left ankle, and coach Jeff Fisher said an MRI exam showed a sprain that likely will keep him out of Tennessee's third exhibition at Atlanta.

But the rookie said he's a fast healer and hopes to return quickly enough to play Friday night. Hawkins caught two passes for a team-high 70 yards in the Titans' 17-16 win against Oakland, including a 51-yard touchdown for his first in the NFL.

Buffalo tight end Derek Schouman missed practice and is out indefinitely with a strained left knee, all but ending his chance to win the starting job out of training camp. Coach Dick Jauron said trainers informed him that it will be weeks before Schouman is expected to be cleared for practice, meaning the player likely will miss the Bills' two final preseason games.

Brett Favre was having fun again. His tearful retirement and tumultuous offseason were tucked away in his memory. Favre was back where he has always been happiest: in the huddle with thousands of cheers providing a perfect soundtrack.

Saying it felt "a little weird" wearing a Jets uniform, Favre was on the field for 14 plays and coach Eric Mangini said the three-time MVP had between 30 and 40 plays to work with.

Jon Kitna completed three passes for 76 yards and a touchdown in the Detroit Lions' 27-10 victory against the Cincinnati Bengals.