Manziel has appeared in four games this season, but he has started only one, a Week 2 victory over the Tennessee Titans.
It was against the Bengals last season that Manziel made his first career start in a disastrous 30-0 defeat, in which he was 10-of-18 for just 80 yards with two interceptions.
"I think a lot of ground has been covered," Pettine said of the progress Manziel has made since then. "I think he's a different player."
"He's been through two weeks of preparation for [Cincinnati in 2014] and on a short week as well. He's drawing from those experiences," McCown said of Manziel. "Just like any work week, we'll work well together to make sure both are prepared and ready to go."
Starting quarterback Josh McCown is dealing with a painful rib injury. Although Pettine said he would wait to name the starter, McCown did not practice Tuesday night in the team's only real on-field preparation for Thursday's game. The Browns would let the 36-year-old start if he recovers by Thursday, but McCown said he felt worse Tuesday than Sunday and everyday activities such as breathing and sleeping were a challenge.
The Browns face the AFC North-leading Cincinnati Bengals on a short week, which limits McCown's chances of returning in time to play.
"There's different things here and there to try to help, but some of it gets chalked up under the pain tolerance type of thing -- and time, more than anything," McCown said. "Right now, we don't have that on our side, as far as this game or, really, this season, because you need probably a little longer than a few days or a few weeks to let this heal."
Information from ESPN.com Browns reporter Pat McManamon contributed to this report.