Joe Berger was doing more than keeping the center spot warm for injured starter John Sullivan when he received word a month ago that Sullivan could not make his comeback this season, and that the Vikings would continue to rely on him to man perhaps the most physically and mentally demanding position on the offensive line.

“Everybody was hopeful [Sullivan would return] throughout the whole process and it just came down to the final MRI that showed [he couldn’t],” Berger said. “You never want to see guys get hurt, but unfortunately that’s part of the game. My role as the [backup], that’s kind of the way it’s been for a while now.”

Berger is respectful of the human element of the next-man-up cliché. But now in his fifth season of being the first guy off the bench here whenever an interior lineman is lost, Berger has carved out a niche and made a nice living being the guy the Vikings turn to whenever disaster strikes — and it always seems to eventually.

“You just have to be ready for it if it happens,” the 33-year-old Michigan native said.

Berger was ready again midway through training camp when Sullivan, arguably the team’s best offensive lineman, had surgery to repair a herniated disk. Berger played well as Sullivan rehabbed his injury. But Sullivan had a setback a month ago and had to undergo back surgery again, officially ending his 2015 season.

So Berger continued to be a bright spot on a patchwork offensive line that has gotten outmuscled on a few occasions, including last Sunday’s 30-13 loss to the Packers, but has blocked well enough for the Vikings to have the NFL’s fourth-ranked rushing attack.

Pro Football Focus, which grades every player in every snap of every game, rates Berger as the third-best center in the NFL this season, behind a pair of former Pro Bowl players in Dallas’ Travis Frederick and Carolina’s Ryan Kalil.

Berger has only been beaten for one sack and has allowed the quarterback to be pressured on just eight plays, tied for the fourth-fewest total among NFL centers, according to Pro Football Focus. Vikings running backs are also averaging 4.4 yards per carry with three touchdowns while running directly behind Berger.

“Joe, I take my hat off to him. He’s an 11-year vet and he’s still playing like he’s in his prime,” right guard Mike Harris said. “I’m happy we have him.”

The Vikings prioritized retaining Berger in the offseason after he had started 18 games at center or guard in his first four seasons here, including nine starts at guard in 2014 after right guard Brandon Fusco tore his pectoral.

Berger, citing a comfort level for himself in the organization and for his family in the Twin Cities, hoped to re-sign with the Vikings, even if it meant that he would have to return to his backup role. And less than an hour before the start of free agency in March, he agreed to terms on a two-year, $2.15 million contract.

“I knew if everything worked out the way it was supposed to, my role was going to be the [interior] swing guy,” Berger said. “And I was OK with that.”

But Berger’s deal, according to a league source, included incentives rewarding him for playing time in the event that he did end up starting for them again.

Berger, who is one of three Vikings who have played every offensive snap this season, will earn $50,000 extra for playing 65 percent of the offensive snaps, a threshold he can reach Sunday at Atlanta, if he hasn’t already. He can make a maximum of $400,000 in incentives if he plays at least 90 percent of the snaps.

The same incentives are included in the second year of Berger’s contract.

This season, with Sullivan out and a young, inexperienced quarterback under center, Berger has proved to be worth every penny the Vikings might end up paying him.

“Smart guys that are extremely dependable and can play a lot of different positions are really, really, really valuable,” coach Mike Zimmer said. “He’s really done a nice job moving in to the center spot. … We didn’t anticipate him being there the entire time, but he’s really been kind of a steadying influence on our offensive line.”