Fullback Zach Line missed the first two days of practice this week, including Tuesday's session, which was the first day of installation of the game plan for Monday night's regular-season opener at San Francisco. How big a deal this is remains to be seen.

A year ago, then-fullback Jerome Felton played only 175 snaps (10.9 per game), according to Pro Football Focus. But Felton's biggest workload — 29 percent of the snaps — came in the season opener at St. Louis, where running back Adrian Peterson played his one and only game of the season.

After Peterson's departure, Felton had only one other game in which he played in at least a quarter of the team's offensive snaps (26 percent). Meanwhile, he had four games in which he played fewer than 10 percent of the offensive snaps.

The Vikings thought highly enough of Line to keep him on their 53-man roster last season. They tried to move him to the practice squad, but had to pull him back when other teams tried to sign him to their active rosters. So he sat behind Felton as the second fullback on a team that barely used a fullback.

That could change some this year with Peterson's return. We'll know more about Line's injury when the first injury report of the week comes out on Thursday. For now, all we know is he stood around for two practices with a wrap on his left knee.

Offensive coordinator Norv Turner didn't sound like a guy who is going to lean heavily on a true fullback this season. But he also said Line serves an important purpose on the team.

"One thing he's showed us is he's quick to the target, he's a physical player and he's a very good athlete so he stays on blocks," Turner said. "There aren't very many plays where his guy made the tackle, in terms of what we're doing.

"We're not a big two-back, fullback in the game team, but it's something we need to be able to do, we need to be able to do it out of our base personnel, we have to do it out of our short-yardage and goal line. There are so many things that you end up with two tight ends and two backs in the game, backed up for a minute. There's a lot of different times you use that different personnel group. He's valuable to us."

Turner also said versatile tight end Rhett Ellison can serve as the fullback if called upon. The team also could make a roster move and promote undrafted rookie Blake Renaud from the practice squad.