There aren't a lot of instances of 41-year-old quarterbacks changing teams, but in terms of 40-year-old-plus future Hall of Fame quarterbacks changing teams, there is a recent track record of success.
In 2009, Brett Favre left the Jets after just one season and led the Vikings to a 12-4 record at age 40. He threw 33 touchdown passes and just seven interceptions.
In 2020, 43-year-old Tom Brady left New England for Tampa Bay. He threw 40 touchdown passes and 12 interceptions, leading the Bucs to an 11-5 record and a Super Bowl title.
Thing is, there have been fewer than 20 quarterbacks in NFL history to even start games after age 40. And most were not their team's primary starter.
Even fewer have been future Hall of Famers. Beyond Favre and Brady, who isn't in yet but will be, the only other 40-plus-year-old Hall of Famer with more than a handful of starts is Warren Moon (11-14 as a starter for Seattle and Kansas City).
Moon was a very good player. But Favre, Brady and Aaron Rodgers are all considered better.
Rodgers, signed by the Steelers Thursday night, threw 28 touchdown passes and just 11 interceptions for the Jets. And the 11 interceptions were a lot for him. Always a quarterback who values the football – Rodgers has 503 touchdown passes against just 116 interceptions in his career – he's reached double digits in interceptions in a season just four times in his 20-year career.
And he'll value the football while producing touchdowns.
Ben Roethlisberger threw 33 touchdown passes in 2020, his first season back after undergoing elbow surgery in 2019.
Since that time, the Steelers have struggled to produce touchdown passes at anywhere near that level.
The Steelers also won't be asking Rodgers to be the Aaron Rodgers of five or 10 years ago. What they need from him is what Favre provided for the Vikings in 2009, when they came within a game of going to the Super Bowl, and what Brady gave to the Buccaneers.