Backup free safety Kurt Coleman turned heads, intercepted a pass and entered the Vikings’ fledgling strong safety competition essentially by default when the Vikings opened the preseason with a 10-6 win over the Raiders at TCF Bank Stadium on Friday night.

With the tentative top two strong safeties on the depth chart — Robert Blanton (hamstring) and Jamarca Sanford (back spasms) — out because of injuries, the Vikings inserted Coleman into the starting lineup alongside free safety Harrison Smith. He played two series with the first unit and then finished the half playing primarily strong safety alongside rookie sixth-round draft pick Antone Exum.

Coleman also had the only takeaway of the game, an interception of Derek Carr’s second-quarter pass that bounced off fullback Jamize Olawale.

“I guess you could say the safeties are pretty much interchangeable,” Coleman said. “There are certain things a free safety has to do and there are certain things a strong safety has to do. But I’ve been going back and forth. So I’m comfortable at both.”

Veteran Chris Crocker, who has played in coach Mike Zimmer’s defense the past seven seasons, didn’t play because he just signed Monday. But he’s expected to become a significant factor in the strong safety competition next week.

The 5-11, 200-pound Coleman isn’t built like the prototypical safety, but he’s also a fifth-year player who started 29 of 59 games for the Eagles before signing with the Vikings this past offseason.

“I think I can add something to this team,” Coleman said. “I have been able to be successful when I do play. So I think there is something to be said about what I’m able to do on the field.”

Peterson sits, Barr sacks

Adrian Peterson was in pads but was the only clear-cut starter who didn’t play. He hasn’t had a preseason carry since 2011. No. 2 running back Matt Asiata started at running back. No. 3 back Jerick McKinnon had a game-high 45 yards on 12 carries.

The only rookie to start for the Vikings, as expected, was ninth overall pick Anthony Barr at strong-side linebacker. He and tackle Ted Johnson shared a sack.

No. 1 ‘D’ shines

For those who might have forgotten what it looks like, the Vikings defense forced a three-and-out on the game’s opening series.

Zimmer, who inherited the league’s worst scoring defense and 31st-ranked pass defense, played his starters for two series. They gave up one first down, no points and held quarterback Matt Schaub to 0-for-2 passing on third down.

“I didn’t know much about what went on last year, being in Carolina and all,” cornerback Captain Munnerlyn said. “But Zim’s said a few times, ‘We got to get better on the back end than they were last year.’ We brought guys in to get better. That’s what we’re doing.”

Continuing his strong summer, rookie seventh-round draft pick Jabari Price came in on third down as the No. 1 nickel cornerback. He played the left outside spot, while Munneryln moved inside over the slot receiver.

Ditto for No. 1 offense

Offensive coordinator Norv Turner’s debut also started well when the offense turned the defense’s opening three-and-out into a 10-play, 70-yard drive that ended with a 1-yard touchdown run by Asiata.

Quarterback Matt Cassel went 5-for-6 for 62 yards to four different targets. That was all the Vikings needed to see of Cassel, who took a seat while rookie Teddy Bridgewater came in to play with the first unit.

In one series with the starters, Bridgewater led the Vikings to a field goal, going 1-for-2 for 13 yards. But a rookie mistake — holding on to the ball too long and too loosely — led to a strip sack in the red zone.

Quick hits

• Punt returner Marcus Sherels didn’t play because of a hamstring injury.

• Kicker Blair Walsh, who went 2-for-5 from 50 yards and beyond last season, missed wide right from 53 yards Friday.