ESPN's Adam Schefter reported the two sides mutually agreed to part ways, and the Lions are expected to be aggressive in pursuing a trade for their longtime franchise face.
Stafford's trade market is an interesting case that will test the value of a good-but-not-great quarterback leaguewide. There is no question that Stafford is an above-average quarterback when he's on the field. He's posted a quarterback rating of 89.9 or higher in each of the last six seasons and thrown no more than 13 interceptions in that timeframe after being turnover prone early in his career.
Heading into his age-33 season, Stafford is 16th in NFL history in both passing touchdowns (282) and passing yards (45,109). Given the Lions have been playing at a significant talent disparity for most of his career—Calvin Johnson and Kenny Golladay aside, Stafford has been left with a below-average supporting cast—there's an argument to be made that he could even improve with a change of scenery.
However, Stafford has increasingly found himself on the injury report and that should be a concern to teams moving forward. Stafford missed eight games in 2019 with a fractured spine, then played 16 games in 2020 despite thumb, rib and ankle injuries.
This was the ninth time in 10 seasons that Stafford has played 16 games, but he's been far from "healthy" over that timeframe. His continued presence in the lineup is more a testament to his toughness than anything.
The Lions likely won't lack for suitors, even despite those concerns. The Indianapolis Colts stand out as an obvious option, given their status as a playoff team and Philip Rivers' recent retirement. Washington and the Chicago Bears are additional potential options if Detroit is willing to trade Stafford in the conference or division.