SANTA CLARA, Calif. -- At this point, there are too many unsolved variables to figure out what exactly Minnesota Vikings RB Adrian Peterson's lackluster return to the NFL means. Was a rickety offensive line, which got little push against the San Francisco 49ers' defensive front, the primary culprit in Peterson's 10-carry, 31-yard night? Or was his night a product of a 49ers offense that rumbled for 215 yards and kept the Vikings' offense off the field? Or was Peterson still trying to shake off rust after 53 weeks without contact?

Those answers will become clearer in the coming weeks, but what seemed clear Monday night was how awkward the Vikings' offense looked with Peterson taking handoffs in the shotgun next to Teddy Bridgewater. The running back had spent most of his NFL career lining up 7 yards deep in the backfield, hitting the line of scrimmage with a full head of steam and effectively daring defenders to bring him down. Lined up next to Bridgewater, however, Peterson had few opportunities to hit the line in stride and give himself a chance to break a big run. He admitted after the game he felt "a little hesitant a couple of times coming out of the shotgun."

According to ESPN Stats and Information, Peterson only ran 40 times out of the shotgun in 2012 and 2013, averaging 4.93 yards per carry. That's a solid figure, though it's nearly half a yard below Peterson's overall average (5.36) and his figure with the quarterback under center (5.39).

"You really just need to be more patient, allow the pulling guard to get on his block and hit it up in there," he said. "Those are the ones I felt like I was kind of hesitant on. I really wanted to hit like I was coming out of the I formation."

That's probably the most revealing thing Peterson said Monday night, and it will be interesting to see whether he, or the Vikings' scheme, moves more to accommodate the other one in coming weeks.

The Vikings' offense has -- probably rightly -- changed to suit Bridgewater, and Jerick McKinnon and Matt Asiata combined for more shotgun carries last season than Peterson had logged in his five previous seasons, according to ESPN Stats & Information. Peterson will probably get more comfortable with the system over time, and the Vikings will have chances to find runs where Peterson can hit the line heading downhill. But after a preseason in which Peterson didn't play -- and a long layoff that saw the Vikings' offense change in his absence -- his long-anticipated return devolved into a downer of a night.

"It's different, because I have to get that speed (from a shallower start)," Peterson said. "But you can be successful. The guys did a great job with it last year, and I feel like I can run in any type of formation. If we continue to work on the things we need to work on, we will improve."