MANKATO - Letroy Guion's transition to nose tackle shouldn't be delayed by more than a week, Vikings coach Leslie Frazier said Sunday morning as the team returned to practice following Friday night's 17-6 preseason-opening loss at San Francisco.

Guion, the former backup to under tackle Kevin Williams, sprained the posterior cruciate ligament (PCL) in his right knee in the first quarter. He sat out Sunday's light indoor practice and will be sidelined through Friday's second preseason game against the Buffalo Bills at Mall of America Field.

"You don't really want him to miss a whole lot of time, because he's a guy that we are counting on to really be a factor for us at that position, a major factor," Frazier said. "We should get him back for the third preseason game."

Guion said he hurt the knee when he banged it on the turf at Candlestick Park.

"It didn't seem that bad at first," he said. "But I went a couple of plays, and it started getting stiff on me."

Guion is trying to overcome the perception that he's undersized for the position that big Pat Williams once locked down so well.

"It's been a great adjustment," he said. "I feel like I'm doing good. Running around, playing double teams and doing everything I need to do to put myself in a great position. I can do a lot of great things in the 'A' gap. Quickness, speed, power. I can hold it down in the 'A' gap."

Brinkley struggled

Jasper Brinkley, whom the Vikings have high expectations for at middle linebacker, played Friday night like a guy who hadn't seen live game action in 355 days.

"He wasn't quite as sharp as we'd like for him to be," Frazier said of Brinkley, who missed the entire 2011 season because of hip surgery. "It wasn't all unexpected, just because of the time lost. It's hard to simulate game speed, even though this is preseason and we all know it's going to ramp up another gear on Sept. 9. But he needed that on Friday night. He needs it again this Friday [against Buffalo]. He hasn't been in those game situations in quite a while."

Before being held to just one assisted tackle at San Francisco, Brinkley hadn't played since Aug. 20, 2011, when he had six tackles in a 20-7 preseason win at Seattle.

Webb gets pass on play

Frazier didn't sound too concerned about the play of backup quarterback Joe Webb, who completed just four of 11 passes for 20 yards while being sacked twice Friday night.

"He was in a tough situation at times with some of the guys that were in the game while he was in there," Frazier said. "But we have confidence in Joe. He'll have enough opportunities this week against Buffalo to get some extended snaps. Looking forward to him to continue to move forward and play a little bit better. I think he will."

Frazier also indicated that the Vikings aren't going to show their entire Webb package in the preseason.

"We have some things, that when the time comes, we can explore his many capabilities on the edge to put pressure on defenses as we've all seen," Frazier said. "We're not going to limit him to just being a drop-back guy."

Start for rookie Smith?

Frazier hinted that rookie first-round draft pick Harrison Smith will get a start Friday when the Vikings play the Buffalo Bills in Week 2 of the preseason at Mall of America Field.

Frazier said coaches watching the tape of Friday night's game continued sensing that the feisty Smith is making a push to get more work with the first team. Up to this point, he's had only limited reps with the starters.

"We're going to do some things a little bit different with the starting rotations on Friday night," Frazier said. "He's done enough now where we feel confident that he can go out there in a starter's role, and we want to see how he performs in that role. He very well could start Friday. He did some good things when he was in there Friday night."

Quick hits

• Frazier said one of his favorite highlights from Friday was having only one penalty called when the offense and defense were on the field. "We had a heavy emphasis in that area," Frazier said. "We didn't like the penalty on special teams, but we're heading in the right direction."

• Right guard Geoff Schwartz, who had sports hernia surgery last week, is back with the team. He's expected to miss four to six weeks.