Conner, who sustained a shoulder injury to his AC joint in the final minutes of Monday's victory over the Dolphins, didn't practice all week after rushing for 145 yards and a touchdown.
In Conner's place, Jaylen Samuels took first-team reps, and he figures to be the starter on Sunday.
"That's what I'm preparing for," Samuels said. "I don't know what James' situation is. I know he's trying to get better and get back as quick as he possibly can. If he doesn't go, then I'll have to be the man."
Samuels missed the past two games after undergoing arthroscopic knee surgery in early October.
"Jaylen Samuels' availability is right on time," coach Mike Tomlin said earlier in the week.
Although he hasn't done it this season, Samuels is plenty capable of shouldering the load at running back. He had double-digit carries in a three-game stretch last season, including 19 carries for 142 yards against the New England Patriots.
This season, Samuels has 18 carries for 50 yards and a touchdown, and he was heavily featured in the Steelers' Monday night win against the Bengals in Week 4. Running out of the Wildcat formation, Samuels had 10 carries for 26 yards and his lone score of the season.
"He's a slow runner," center Maurkice Pouncey said. "He reads the holes the right way, and then he's an upfield guy. It always seems like he's always falling forward. Whenever you see that as a lineman, like man, that's a good back."
And with eight receptions for 57 yards in the Bengals win -- and 12 receptions for 81 yards on the season -- Samuels can also be a threat in the receiving game.
"He's really unique as a pass-catcher, a route runner," offensive coordinator Randy Fichtner said. "He's nifty in a lot of ways. We know he can be capable of being that one back that can play all three downs. He's done it before in big games. I think back to New England last year. I mean, he's had plenty of those moments. So, I'm just excited to have him back."
While Conner hasn't been officially ruled out, backup running back Benny Snell and starting left guard Ramon Foster are definitely not taking the field Sunday. Foster was ruled out with a concussion, while Snell is out with a knee injury, leaving backup duties to Trey Edmunds, who was on the practice squad earlier this season.
"He's got a consistent run demeanor," Tomlin said of Edmunds. "He's tough. He's downhill. He finishes plays aggressively. All those things we like, and he's got solid consistent ball security."
Conner and Snell are the team's top two rushers with 380 yards and 118 yards, respectively. After a slow start to the run game, the Steelers have improved in the past two games. After averaging 67 rushing yards a game in the first five weeks, Pittsburgh's ground game surged with 168 rushing yards against the Dolphins and 124 against the Chargers. Now, it'll likely be up to a new tandem in Samuels and Edmunds to keep the momentum going.