Tests confirmed Browns Pro Bowl center Alex Mack fractured his fibula in Sunday's 31-10 win over the Steelers.
Mack is likely to undergo surgery that will all but end his season. After Mack was carted off the field, John Greco moved over to center, it would be the first time in Alex Mack's six-year NFL career that he missed a snap.
Browns Head Coach Mike Pettine said he will get together with General Manager Ray Farmer to determine their next move.
Mack signed a five-year, $42 million deal with the Browns, making him the highest paid center in the NFL.