John Sullivan's prognosis

Per Tom Peliserro of 1500ESPN.com, Minnesota Vikings center John Sullivan is recovering from microfracture surgery on his left knee. Because the surgical legion was small, he is expected to require only three to four months of rehab. It's a bit of a surprise that Sullivan had such a problem with the joint, because there were no signs that he was ailing last season.

"Sullivan was listed on the Vikings' injury report with a knee issue only once this season, before their Week 13 game against Chicago. He also appeared with rib and ankle injuries but played all 1,097 gradable offensive snaps," Peliserro wrote.

"If Sullivan's performance suffered because of his health, it wasn't obvious. The website ProFootballFocus.com graded him as the NFL's No. 1 center, and he was named a first alternate for the NFC's Pro Bowl roster."

Based on this initial timeline for recovery, he should be fine for training camp. However, players who undergo microfracture surgery often take a full year or more to get back to full speed, so his health will be something to keep an eye on as the season nears.