Kirk Cousins was a good quarterback in 2015, and a very good one in 2016. He will probably be a very good quarterback for the Redskins again in 2017, and then will likely switch teams after the 2017 season. He will turn 29 this August, which means he would be 29 years old in the year before switching teams, and turn 30 in preseason next year with (presumably) a new team. That’s because the Redskins and Cousins can’t seem to come to terms on a long-term deal, and with Washington unlikely to tag Cousins again after the season, he will be free to move to another team.  And that will make him the extraordinarily rare case of a quarterback in his prime years hitting the open market.

Using my era-adjusted passer ratings, looked at all quarterbacks who had an above-average rating during a season in his twenties and then switched teams in the off-season. The two with the highest era-adjusted passer ratings before switching teams? Drew Brees with San Diego in 2005 and Neil O’Donnell with the Steelers in 1995.  Both left as free agents, with Brees going to New Orleans and having a Hall of Fame career, and O’Donnell going to New York and… playing for a 1-15 Jets team.

The others? Jason Campbell was traded from Washington to Oakland after 2009, after first signing an offer sheet with the Raiders.  Campbell was a solid quarterback, but losing him wouldn’t be nearly as big of a deal for Washington as losing Cousins.  In other trade scenarios, Matt Cassel was also traded from New England to Kansas City after 2008, and Jay Cutler was traded from Denver to Chicago.  Both players were viewed as potential stars, but neither hit the open market, either.

Three other mediocre quarterbacks made the cut on the basis of leaving after good seasons: David Carr went from Houston (after his best season) to Carolina after ’06 to be the Panthers backup quarterback, Brian Griese left Denver to be a backup in Miami after 2002, and Gus Frerotte left  Detroit for Denver in 2000.

Jeff Blake had a long run of average play from ’94 to ’99 in Cincinnati at the ages of 24 to 29.  He then became a significant free agent to switch teams, choosing to sign with New Orleans. Craig Erickson had numbers that look much better than you would have thought in 1994, but with Trent Dilfer having been a first round pick that year, the Bucs traded him to Indianapolis after the ’94 season.

That’s my list of passers to switch teams in their 20s after an above-average season.   What else do you think?