Tom Brady was 40 years old when the Patriots traded his backup, quarterback Jimmy Garoppolo, to the 49ers in October 2017. That sounds ancient for a QB in the NFL.

Not for Brady, though.

The legendary quarterback reportedly agreed to a two-year contract extension with New England on Sunday. Brady would have become a free agent after the 2019 season, but ESPN's Adam Schefter reported the two sides came to an agreement that will keep him with the Patriots through the 2021 season.

Brady, who turned 42 years old Saturday, will receive an $8 million raise this season, pushing his salary from $15 million to $23 million. He now is the sixth-highest paid quarterback in the league and will make roughly $6 million more than Garoppolo.

When the Patriots selected Garoppolo in the second round of the 2014 NFL Draft, he looked like the quarterback of the future in New England. Brady was months away from turning 37 years old and was coming off a season where he threw his lowest amount of touchdowns since 2009.

It's clear now, Garoppolo never stood a chance in New England. As long as Brady still is playing football, his backup is simply a backup, not the heir to the throne.

Since the Patriots drafted Garoppolo, Brady has won three Super Bowl rings. On the other side of the story, Jimmy G signed a monster five-year, $137.5 million contract with the 49ers in February 2018, but only has 10 starts under his belt in the NFL.

[RELATED: 49ers' remodeled defensive line has impressed Garoppolo]

Garoppolo's time is now with the 49ers. Brady's time will last for as long as he straps on shoulder pads under a Patriots jersey.