Vikings center John Sullivan had microfracture surgery on his left knee last week, according to 1500 ESPN.
Sullivan, who played in every offensive snap last year and was a first alternate for the Pro Bowl, is expected to have a three- to four-month rehabilitation and be available for training camp, according to the report.
He will likely not be available to practice for most, if not all, of the Vikings' offseason program. The team's offseason conditioning program starts on April 22, with organized team activities to follow and then minicamp, which is expected to be in mid-June.
Sullivan has played in all but three games in his five-year NFL career, missing one game in 2011 and two in 2010. He has been the team's starting center since 2009, after Matt Birk left for Baltimore via free agency.
Microfracture surgery is used to repair the articular cartilage by creating tiny fractures in the underlying bone, causing new cartilage to develop.
Defensive end Jared Allen (shoulder) and punter Chris Kluwe (knee) also had surgeries this offseason.
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Report: Sullivan has microfracture surgery
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