Three-time Pro Bowl center Maurkice Pouncey was carted off the field in the first quarter after sustaining an apparent right knee injury. Teammate David DeCastro dove on a cut-block attempt but missed his intended target and drilled Pouncey directly in the back of the leg.
NFL Media's Aditi Kinkhabwala reported that Pouncey was being taken to a hospital for an MRI on Sunday.
Tomlin is operating under the assumption that both players will be lost for the season.
Pouncey's absence is a severe blow to the Steelers' run blocking and pass protection. The offense tanked after losing their best lineman, failing to move the ball consistently for the final three quarters.
Kelvin Beachum, a seventh-round draft pick last year, will take over as the starting center.