Although Roethlisberger expressed confidence that his bruised elbow would not prevent him from playing against the Chiefs, sitting out Thursday's practice led to some doubts.
"We'll see how I feel tomorrow," said Roethlisberger, per ESPN.
Asked Thursday whether he expected Roethlisberger to be under center Sunday, Steelers offensive coordinator Randy Fichtner told the NFL Network: "I wouldn't be able to answer that at this point."
Pittsburgh released longtime backup Landry Jones just prior to the season. Backup Joshua Dobbs took all the first-team snaps at Thursday's practice.
A fourth-round draft pick out of Tennessee in 2017, Dobbs has never appeared in an NFL game. He threw for 2,946 yards with 27 touchdowns and 12 interceptions in his senior year with the Volunteers.
Roethlisberger, who routinely doesn't practice on Wednesdays, injured his elbow on the penultimate offensive play in the Steelers' 21-21 overtime tie with the Cleveland Browns on Sunday.
The six-time Pro Bowl selection completed 23-of-41 passes for 335 yards with one touchdown and three interceptions against the Browns. He also lost two fumbles on sacks.
A two-time Super Bowl champion, Roethlisberger has been Pittsburgh's starter since he was drafted in the first round in 2004.