EDEN PRAIRIE, Minn. -- Adrian Peterson has been cleared for takeoff.

The reigning NFL MVP will make his preseason debut against the San Francisco 49ers this week, Minnesota Vikings coach Leslie Frazier said on Sunday. Peterson sat out the first two games against Houston and Buffalo and hasn't played in an exhibition game since 2011. The Vikings held the star running back out of all four games in the preseason last year while he worked his way back from reconstructive surgery on his left knee.

Frazier wasn't ready to divulge exactly how much Peterson will play at San Francisco, but there is no question that his mere presence should be a boon to a starting offense that looked awfully ragged in its first extensive playing time of the preseason at Buffalo last week.

Adrian Peterson has been relegated to the preseason sidelines for the Vikings since 2011, but will take the field for the team's tune-up against the Niners. Kevin Hoffman/USA TODAY Sports

"Without Adrian Peterson in our scheme, it impacts our offense tremendously because he's the focal point," Frazier said. "Yeah, it definitely makes a difference. That will be obvious when we open up the season. It's obvious if you look at us from a season ago and it showed on Friday night."

After playing just two plays in the exhibition opener against Houston, Christian Ponder and the rest of the starting offense sans Peterson played five series against the Bills. Ponder went 5 of 12 for 53 yards, was sacked on the first play of the game and also took a 14-yard loss when center John Sullivan fired a shotgun snap when Ponder wasn't looking. The offense failed to get a first down on four of the five possessions while Ponder was in the game and managed just three points.

For a young quarterback who is throwing to a new-look set of receivers and has been dubbed as the single biggest factor in the team's hopes to return to the playoffs for a second straight season, it did little to show he was poised for a breakout season. The Vikings also dropped several passes and the offensive line looked completely unprepared for the Bills' exotic blitzes, so there was plenty of blame to spread around.

"There's a lot of things we're going to be able to learn from the tape, and I think next week in San Francisco is going to be the big barometer of where we are as a team," Ponder said after the game. "I think the starters will play the first half and a little bit into the second half. So we'll learn from this one and move on to the next one."

It is unlikely that Peterson will play that deep into the game against one of the league's toughest defenses. But just getting him out there at all will be a change of pace from last year. Peterson was working on coming back from a horrific knee injury in December of 2012, and the Vikings weren't about to take any chances with the face of their franchise.

Even though Peterson lobbied to get a little playing time so he could get back into a rhythm, sitting all four games didn't hurt him one bit. He rushed for 2,097, nine yards shy of Eric Dickerson's single-season record, and 12 touchdowns, with eight runs of at least 40 yards in a jaw-dropping comeback season. He carried the Vikings into the playoffs, where they lost to the Green Bay Packers in the first round.

As important as Ponder's progress is to the team, everyone knows that the Vikings' offense starts and ends with Peterson. That's why it wouldn't have been surprising to see Peterson sit out the entire preseason for a second straight year to avoid the risk of injury and rest up for what no doubt will be another high-carry season. But Frazier said he wants to see Peterson out there next Sunday night, which will give coaches a chance to evaluate the offense as a complete unit.

"We want to be a balanced offense," Frazier said. "But as anyone that follows us knows, our offense is going to be run through No. 28, through Adrian."

Whether he plays for a series, a quarter or a half, and whether he gets one carry or 10, there is no doubt that having Peterson in the backfield gives the offense a confidence that it does not have when he's on the sideline.

"That's our back and we definitely would like to have him out there, without a doubt," right tackle Phil Loadholt said.

NOTES: Frazier said reserve DT Christian Ballard has been put on the active/left squad list. Ballard left the team for personal reasons last week. Frazier said they will evaluate the situation further as they get closer to final cut-down day. ... LT Matt Kalil (knee) and WR Jarius Wright (concussion) did not practice on Sunday. Frazier said he didn't think either injury was serious and both players will be evaluated as the week progresses. ... Rookie first-round pick Sharrif Floyd (knee) also did not practice and will be examined further on Tuesday.