Vikings' John Sullivan reportedly has knee surgery

John Sullivan of the Minnesota Vikings was ranked as the No. 1 center in the NFL by Pro Football Focus in 2012. While fullback Jerome Felton and offensive tackles Matt Kalil and Phil Loadholt garnered plenty of attention, Sullivan flew under the national radar while paving the way for Adrian Peterson's MVP campaign.

The Vikes are now expected be without Sullivan for the majority of their offseason program. ESPN Twin Cities reported the 27-year-old underwent "relatively minor" microfracture surgery to repair a small lesion in his left knee last week.

While microfracture surgeries have been known to derail players' careers and are frequently accompanied by setbacks, the Vikings are reportedly confident that Sullivan will be ready for the start of the 2013 season.

For Peterson's sake, that better be accurate. If he's going to make another run at Eric Dickerson's single-season rushing record, he's going to need his standout center at full strength.

Follow Chris Wesseling on Twitter @ChrisWesseling.