Backup quarterback is one of the weirdest positions in all of sports. You want to have enough talent behind your starter that if he goes down the seasons isn’t a wash, but not enough talent that after every interception your fanbase is calling for the backup. It is a fine line to walk, and most teams opt to have an experienced veteran or young up-and-comer behind their number one guy.
For three years, the Dallas Cowboys have had Cooper Rush backing up Dak Prescott. Rush does not really fall into either category of experienced vet or promising up-and-comer.