It's rare for an NFL quarterback to join a new team and promptly lead that squad to the NFC championship game, as Tom Brady has done for the Tampa Bay Buccaneers. His team will visit Lambeau Field and the Green Bay Packers with a Super Bowl berth on the line Sunday.

Since the AFL-NFL merger in 1970, 12 quarterbacks have led a team to the league championship game one year after playing professionally elsewhere, and of those, five have pushed their team as far as the Super Bowl (though one defeated another quarterback in the same boat to get that far). Two won the Super Bowl, and a third won a ring though he didn't play in the final showcase.

Many of these quarterbacks were signed as backups initially.

2019 season: Ryan Tannehill, Tennessee

After six largely unremarkable years in Miami, Tannehill found a groove in his first year with the Tennessee Titans. He completed a career-best 70 percent of his passes and guided the Titans to a pair of playoff shockers, wins over New England and Baltimore. The road ended there in a 35-24 loss to Kansas City in the AFC championship. 

2017: Case Keenum, Minnesota

The journeyman had already played for three other teams in his five NFL seasons, but the Vikings won 11 of his 14 starts in 2017 when he threw for 22 touchdowns and only seven interceptions. Keenum had originally been signed as a backup to Sam Bradford; the Vikings still didn't know when Teddy Bridgewater would be back after he suffered a gruesome leg injury in 2016. But Keenum seized the reins after Bradford was hurt in Week 2, though Keenum was outplayed by another newcomer in the 2017 championship game.