With Anderson unsigned and hoping to land somewhere as a free agent, Rivera said at Tuesday's organized team activities that Carolina's backup quarterback will come from the group of players already on the roster, according to the Charlotte Observer.
Anderson, who will turn 35 next month, attempted eight passes or fewer in five of his seven seasons with the Panthers. He made four starts with Carolina, losing both in 2016 and winning both in 2014.
The three quarterbacks behind Newton have attempted a combined one pass in the NFL. Garrett Gilbert, a sixth-round draft choice of the Rams in 2014, is considered the front-runner for the backup job.
Also in the mix are former Houston Texans quarterback Taylor Heinicke and undrafted rookie Kyle Allen out of the University of Houston.
Newton has been among the most durable quarterbacks in the league, missing just three games due to injury in his seven seasons.