Vikings C John Sullivan underwent microfracture surgery on his left knee last week, according to PFW correspondent Tom Pelissero of ESPN 1500.

Sullivan is facing a 3-4 month rehab. Sources told Pelissero that Sullivan had a small lesion and should make a full recovery before training camp.

In 2012, Sullivan played every snap and was considered one of the league’s top centers. In five seasons with Minnesota, Sullivan has played in 77 games with 61 starts.