Vikings General Manager Rick Spielman made one heck of a trade in the first week of September. The Sam Bradford deal wasn't bad, either.

On Sept. 5, 2015 — 363 days before he made the blockbuster deal to acquire Bradford from Philadelphia — Spielman made absolutely no headlines whatsoever when he sent a sixth-round pick to the Chargers for Jeremiah Sirles, an undrafted rookie in 2014 with one career start and the potential to play all five offensive line positions.

"We knew when he came in last year that he could play different positions," Vikings center Joe Berger said of Sirles, who is threatening to make Berger the team's second-most versatile offensive lineman. "But you never know what you got until you throw him in there. It's not my job to judge, but he looks like he's doing pretty well."

In the 22-10 upset at Carolina, Sirles played the final 39 minutes at left guard when Alex Boone went down because of a hip injury. The Vikings outscored Carolina 22-0 with Sirles on the field.

Boone returned and was dominant in Monday's 24-10 victory over the Giants at U.S. Bank Stadium. But right tackle Andre Smith went down because of an elbow injury with eight minutes left in the first quarter.

Smith said after the game that he will be fine for next week's game against Houston. If not, things might still be fine.

With Sirles on the field for the final 52 minutes, the Vikings scored 24 points, didn't give up a sack, finally surpassed 100 yards rushing and scored their first two rushing touchdowns of the season.

Going to Week 5, the Vikings and Broncos are the NFL's only 4-0 teams. And the Vikings' most valuable lineman in a season of turmoil up front just might be the 6-6, 315-pound kid wearing Matt Birk's old number.

"Hey, the more you can do, the more you can stay," Sirles said. "I prepare as if I can play all five positions because you just never know. The ability to do that is something I mentally pride myself in."

The Vikings offensive line has been bleeding since the eve of training camp when right tackle Phil Loadholt had to retire. Guard Mike Harris showed up with an undisclosed illness and still hasn't suited up. Center John Sullivan couldn't return to form from two back surgeries and was released. And Matt Kalil dropped two weeks into the season and was placed on injured reserve, forcing T.J. Clemmings into a position he'd never played before in a regular season.

Yet, here we are, watching an offense operate about as efficiently as possible considering its starting quarterback went down with a season-ending knee injury 18 days before the opener and its Hall of Fame running back followed him to injured reserve a month later. The Vikings offense still has not turned the ball over a month into the season. Amazing.

"We've had a lot of guys step in," Berger said. "I've never had to go out to tackle. But I know just switching from guard to guard is difficult. I can imagine going guard to tackle on the other side is very difficult."

And all it cost Spielman to bring Sirles in for depth purposes was a sixth-round pick in this year's draft. Sirles didn't play last season, but is he ever paying off this season.

The Giants spent $200 million to improve their defense this past offseason. Yet no one could match Sirles and his linemates.

On Jerick McKinnon's 4-yard touchdown run, the Vikings used a power formation that moved Clemmings over to the right side next to Sirles.

"The [end] lined up in a five-technique, and me and T.J. just kind of looked at each other and thought, 'We're going to move this dude and we're going to score,' " Sirles said. "And we moved him off the ball and Jerick fit it up right behind us and we were able to pound one in. It was fun, definitely, getting a running touchdown like that."

Mark Craig covers the NFL and the Vikings for the Star Tribune.

Twitter: @MarkCraigNFL • mcraig@startribune.com