Vikings coach Leslie Frazier said the team knew fullback Jerome Felton might be subject to a suspension when they re-signed the Pro Bowl fullback during the offseason.

Felton's three-game suspension was announced by the league Monday, the result of his DUI charge in 2012, which was ultimately reduced to a careless driving charge.

Felton, who is also recovering from an appendectomy, attended Monday's practice but did not speak with the media.

"Going into training camp we had an idea it could possibly happen," Frazier said. "We didn't know the extent, but we knew the possibility.''

Now the team is concentrating on who might fill in for Felton, whose lead blocking for Adrian Peterson earned the new contract. Frazier talked about using Rhett Ellison and perhaps rookie Zach Line as replacements.

Ellison has impressed the coaches with his work ethic since being taken in the fourth round of the 2012 draft.

"He's one of the hardest working players on our team," Frazier said. "It's hard to outwork Rhett. He comes prepared every single day. Seeing his work ethic his rookie year, I was so impressed. … He has not let up from his rookie season. He'll be ready when we line up against Detroit. But yes, we could add more to his plate, and we probably will have to now."

Bishop improves

Frazier said he was impressed with the improvement linebacker Desmond Bishop made from the team's second preseason game to the third. Sunday, getting heavy playing time, including some snaps with the No. 1 defense, Bishop led the team with nine tackles, all solo, two for loss, against the 49er. Bishop continues to push for a starting position.

"We're going to play him on Thursday night [against Tennessee] and you'd hope he'd get better again," Frazier said. "He showed some things."

Down to the wire

It appears Joe Webb and Stephen Burton could be fighting for the final receiver spot.

Burton had an up-and-down game Sunday. He caught three passes for 31 yards, but also stopped on a slant route, leading to an interception of a Christian Ponder pass. Webb made only one catch, but it was a nice one, leaping high to make a 3-yard TD grab.

"You want guys to continue to impress," Frazier said. "We want [Burton] to get better. We want Joe to get better. We want that decision to be a tough decision."

No fine, no repeat

Vikings receiver Jerome Simpson won't be fined for leaving the sideline to trip a fan who was running loose on the field Sunday in San Francisco.

"I'm pretty sure he was surprised," Simpson said after Tuesday's practice. "He did not expect that."

But, Simpson said, he probably wouldn't do it again.

"That's something I probably shouldn't have done," he said. "I talked to Coach about it. Just let the security do their job. That was kind of a mistake on my part.''

Etc.

• Receiver Greg Childs, who is recovering from patellar tendon surgery to both knees, was put on the regular-season physically unable to perform list, which means he won't be able to practice or play with the team until after the first six regular season games.

• A number of players were held out of practice Tuesday, including cornerback Chris Cook (groin), defensive tackle Sharrif Floyd (knee procedure), linebacker Erin Henderson (left heel), receiver Cordarrelle Patterson (soreness) and safety Mistral Raymond (AC sprain in his shoulder). Raymond is doubtful for Thursday's game. Veteran receiver Greg Jennings was also held out of practice, as was Burton, for unspecified reasons.