Adrian Peterson spotted his opening, an inviting swath of running room that he ordinarily turns into a personal highlight.

On the second play of Sunday’s game at Seattle, Peterson took the handoff and started left. He hit a wall of bodies so he stopped, saw open field to his right and accelerated.

But he staggered slightly as he reached for his extra gear, and Seahawks safety Earl Thomas came racing in to make the tackle. Peterson picked himself up slowly after a 7-yard gain.

That play underscored that this is not Adrian Peterson circa 2012. First hamstring tightness and now a nagging groin injury have sapped Peterson of some of his normal burst and explosiveness.

What if he was healthy and had that same exact scenario?

“I’m out of there on that play,” he said.

In other words, the play would have resulted in a big gain. Granted, Thomas is an All-Pro safety and one of the NFL’s best defensive players, but the way that he brought Peterson to the ground demonstrated that the NFL’s reigning MVP is not himself these days.

“It wasn’t frustrating, it was just disappointing,” Peterson said. “The main thing was to be out there helping my team. I was putting my best foot forward. But there were a couple of plays where I was like, ‘Wow, if I had that explosion, it would be a different turnout.’ ”

Peterson, however, refuses to take a seat for even one game in order to recover. He missed practice for a second consecutive day Thursday, but he said he expects to play Sunday against the Green Bay Packers at Lambeau Field.

That will mark Peterson’s 100th career game, a milestone he mostly downplayed except to call it a “blessing.” Peterson thinks it would be “crazy” if anyone — even his coaches or medical staff — suggests that he takes a game off to recuperate.

“I’d be like, ‘Well, I know my body and I’m not going to do anything to hurt myself. Just trust me,’ ” he said.

Both fullback Jerome Felton and offensive coordinator Bill Musgrave seemed bemused by the suggestion that Peterson should rest since the 2-8 Vikings are out of the playoff picture.

“That’s not how he is,” Felton said.

“I don’t think that’s part of his fabric,” Musgrave said.

Durable back

Peterson speaks from experience. He’s been listed on the official injury report 38 weeks in his career, but he’s been declared out at the end of that week only twice. In all, he’s missed only seven games in his career, despite absorbing a physical pounding that comes with carrying the ball 1,948 times.

His injuries this season have limited his ability to practice. Instead, he joked that he “lives with [head athletic trainer] Eric Sugarman for the entire day” as he gets his body prepared to play on Sunday. The “push to Sunday,” as he calls it.

“Most important,” Peterson said, “is just kind of letting the body rest.”

Peterson dealt with hamstring tightness for several games, which he admitted caused him to run hesitantly. The groin problem landed him on the injury report last week.

Peterson refuses to concede anything, but injuries obviously have affected his game, most notably in explosive runs. Peterson compiled 27 runs of 20-plus yards last season. He has only five this season.

That sharp decline also can be attributed to inconsistent play by the offensive line and a passing game that doesn’t scare opposing defenses.

Still a chance

Peterson’s long-term health is an organizational priority since he signed a seven-year contract extension worth a maximum of $100 million in September 2011. But he disagrees with anybody who suggests that he should take time to get healthy because the Vikings season looks like a lost cause.

“In my eyes, I don’t know how you all think, but I still think we’ve got a chance,” he said. “Call me crazy. But I still feel like we have an opportunity. That’s the way I’m going to approach this week and the rest of the season.”

Based on what?

“The guys that are in this locker room,” he said. “I feel like I believe in every guy in here, and I believe in [quarterback] Christian [Ponder]. I believe that he can turn it on and get into a run. I have faith in the guys in this locker room. When I look in these guys’ eyes, when I’m on the field with them, they’re playing their hearts out. They’re out there competing. I don’t see guys quitting.

“So with that, you still have a chance. I choose to focus on that opportunity and that chance that we have and believing in these guys in this locker room and really don’t care what everyone else on the outside thinks about it. That’s just how I look at it.”