Browns coach Mike Pettine would not confirm whether he has decided to start Manziel, saying Monday that he still has not talked to the team's quarterbacks about his plans.
While a team spokesman said he had no knowledge that Manziel would be named the starter, one source told ESPN that Manziel would replace Austin Davis as the starter unless Manziel had done something to jeopardize his status between the end of Sunday's loss and Monday.
Manziel's start is set to come at home against the San Francisco 49ers on Sunday. Cleveland then closes out its season with games against the Seattle Seahawks, Kansas City Chiefs and Pittsburgh Steelers.
Davis went 25-of-38 for 230 yards with no touchdowns and an interception against the Bengals. He was sacked three times.
The Browns want further evaluation of Manziel's ability on the field and how he handles any success and failure off it, a source told ESPN. Even then, the sources said, the Browns are uncertain whether Manziel can re-establish the hope the franchise had when it made him a first-round pick in 2014.
Manziel was demoted to third-team quarterback after being disciplined for his decisions during the team's bye week and because he lied to the coaching staff about a video that appeared of him partying in an Austin, Texas, nightclub.
Josh McCown returned as the starter in Week 12 but suffered a season-ending broken collarbone and was replaced by Davis.