The decision to go with Newton for the second straight game doesn't mean he will be the Week 1 starter in the regular season, Rivera said.
"The big thing that we have to do is continue to evaluate the situation and circumstances. We've only really gone through about three and a half, four weeks of training camp, so to rush into a decision I think would be kind of absurd," Rivera said on Sunday. "What we want to do is see how he handles this whole game week preparation."
The coach said Newton will probably play three quarters against the Bengals, depending on how things go.
"What it will do is give us an opportunity to see how he'll handle the whole game experience, and we'll go from there," Rivera said.
Newton, the No. 1 draft pick out of Auburn, got his first NFL start and played the entire first half in a 20-10 loss to Miami on Friday. He was 7-of-14 for 66 yards.
Rivera has said all along that it was his plan to rotate preseason starts among the team's quarterbacks. Newton played behind Jimmy Clausen in his exhibition debut two weeks ago and the team also has Derek Anderson on the roster.