FILE - In this Jan. 31, 1988, file photo, Washington Redskins quarterback Doug Williams prepares to let go of a pass during first quarter of Super Bowl XXII against the Denver Broncos in San Diego. Brock Purdy's bid to join the select group of quarterbacks to go from a backup for most of the season to a Super Bowl starter got derailed when he suffered his own injury in the NFC championship game. There have been several examples of backups leading a team to the big game. (AP Photo/Elise Amendola, File)

FILE - New York Giants quarterback Jeff Hostetler (15) celebrates a second quarter touchdown against the Buffalo Bills during Super Bowl XXV in Tampa, Fla., in this Jan. 27, 1991 photo. Brock Purdy's bid to join the select group of quarterbacks to go from a backup for most of the season to a Super Bowl starter got derailed when he suffered his own injury in the NFC championship game. There have been several examples of backups leading a team to the big game. (AP Photo, File)

FILE - Philadelphia Eagles quarterback Nick Foles throws during the first half of the NFL Super Bowl 52 football game against the New England Patriots Sunday, Feb. 4, 2018, in Minneapolis. Brock Purdy's bid to join the select group of quarterbacks to go from a backup for most of the season to a Super Bowl starter got derailed when he suffered his own injury in the NFC championship game. There have been several examples of backups leading a team to the big game. (AP Photo/Matt Slocum, File)