Clausen lost his starting job to Cam Newton last year and appeared to be on the roster bubble heading into the preseason. He might have saved his job Thursday against the Pittsburgh Steelers, passing for 173 yards and two touchdowns in one half, including a 79-yard score to rookie Lamont Bryant with 2:31 to play in the game.
"I thought Jimmy did a nice job, I really do," Rivera said after the game, via The Associated Press. "Coming in the second half and playing the way he did is indicative of what he's capable of. I was very pleased with that. He made plays at the end ... and put us in position to give us a chance to win a football game."
It remains unclear whether Clausen or Derek Anderson will serve as Newton's primary backup.
Follow Dan Hanzus on Twitter @danhanzus.