EDEN PRAIRIE, Minn. -- Minnesota Vikings center John Sullivan, one day after having back surgery, was placed on short-term injured reserve Thursday.
The 30-year-old Sullivan, who hadn't practiced since Aug. 18 with what the team had termed as back spasms, underwent a lumbar microdiscectomy Wednesday.
The Vikings' already-thin offensive line will have to adjust to the loss of possibly their most valuable lineman until he is eligible to return after eight weeks.
Coach Mike Zimmer said the team had hoped Sullivan, who had been receiving regular treatment -- including two epidurals, would recover without surgery. That, however, changed this week.
"He was doing better," Zimmer said. "He was running. Typically, you treat these conservatively because if you don't, you could end up having the surgery. You want to take your time to see if it heals. And he just got to a point where he was getting better but he couldn't get over the hump."
One of the team's most mobile and effective run-blockers, Sullivan had started all but two games for the Vikings since 2009 and earned a contract extension this offseason. He was a valuable resource to quarterback Teddy Bridgewater during his first season, helping set the Vikings' pass protections at the line of scrimmage.
Joe Berger will start at center in Monday night's opener against the San Francisco 49ers. The team already lost right tackle Phil Loadholt to a season-ending torn Achilles, and it has a new starting right guard in Mike Harris after Brandon Fusco moved to the left side to play next to left tackle Matt Kalil.
Berger started nine games last year, filling in at right guard with Fusco out. The Vikings, though, view center as Berger's natural position. He had practiced with the starting offensive line during the last three weeks.
"To get put in this role, I'm embracing it," Berger said. "I'm looking forward to it, for however long it lasts. We hope John heals up quick and gets back when he can. He'll be missed when he's gone. I know he was working like crazy to try to get back. For whatever reason, the decision came down that this was the right thing to do."
In 2012 and 2013, the Vikings' five offensive linemen played 159 of a possible 160 games. Now, the four linemen from that group who are still on the team -- Kalil, Fusco, Sullivan and Loadholt -- have all had at least one surgery in the past 12 months.