"We've got a great deal of respect for Johnny Manziel and his talents," Tomlin said Tuesday at his weekly news conference. "They didn't draft him in the first round to watch. We fully expect them to utilize him in some capacity in this football game."
Manziel, a ballyhooed rookie, did not unseat Hoyer as the Browns' starter during the preseason, and both struggled at times during the heavily scrutinized quarterback competition.
Hoyer completed 24 of 44 passes for 261 yards and a touchdown with an interception. Manziel completed 30 of 59 passes for 296 yards and two touchdowns.
The former Heisman Trophy winner also rushed for 88 yards and averaged 7.3 yards per carry in the preseason, displaying the scrambling ability that served him so well at Texas A&M.
"Obviously Manziel has some unique run skills and capabilities," Tomlin said. "I think they're capable of highlighting that within the framework of their offense. And it's not like Hoyer is immobile. I don't imagine they're going to be drastically different with either guy in there."
The Steelers are familiar with Hoyer, as he spent part of the 2012 season with them after injuries left the team thin at quarterback.
Hoyer dressed for two games for the Steelers before getting released, and he led the Browns to two wins early last season before tearing an ACL in his third start for Cleveland.
He will try to lead the Browns to their first win in Pittsburgh since 2003 when the teams meet Sunday at 1 p.m. ET.
"He's a consummate professional, he's an energy bringer," Tomlin said. "He's not going to lose games above the neck. What you don't see on tape is probably what's most impressive about him. He's a good football player, and it doesn't surprise me at all that he's the guy that they've chosen to go with."
Tomlin said preparing for two quarterbacks won't make it any more challenging for the players or coaches this week.
"I think all of the things they ask [Manziel] to do Brian Hoyer is fully capable of doing it, and I'm sure they're going to do it with him as well," he said. "I just think when you've got a talent like Johnny Manziel, you're going to get him on the field and help him grow and develop even as you get into the regular season. I don't think necessarily his presence in the game is going to dictate a difference in schematics."