Patriots center Ted Karras is believed to have suffered an MCL sprain last night, a source tells Ian Rapoport of NFL.com (on Twitter). A Monday MRI will confirm the diagnosis, but the belief is that he’ll be able to return from the injury at some point this year. 
Karras has been having a solid year as the Patriots’ starting center, a role that he was not slated for at the outset of the year. In the offseason, Karras was seeing practice reps at left guard, but injuries forced him into the anchor role on the Pats’ offensive line.
Karras, 26, has appeared in 57 games for the Pats over the last four years, but had only five starts to his credit before 2019. This year, he has been first-string for all of his games while allowing just two sacks on Tom Brady, tying him for fourth among all centers. Meanwhile, he’s been flagged for just three penalties across 798 snaps, the third-highest snap count of any center in the NFL this year.
The Patriots are unlikely to have Karras on the field for Sunday’s game against the Chiefs, but they’ll hope to have him back for some of the final regular season games of the year, plus the playoffs.