Ian Rapoport of NFL Network reported Trubisky agreed to a one-year, $2.5 million deal.
While he showed impressive flashes during this stretch, he failed to find any consistency, and his starting job was repeatedly in question. He was benched for Nick Foles for nearly half the 2020 season before regaining his role down the stretch, finishing with 2,055 passing yards with 16 touchdowns and eight interceptions in 10 appearances.
Over his first four years, the 26-year-old has 10,609 passing yards with 64 passing touchdowns plus eight rushing touchdowns.
At his best, Trubisky has shown the ability to impact a game with his arm and legs.
He finished the 2018 season with a 71.0 QBR, third-best in the NFL, while helping the Bears to an 11-3 record as a starter. He also rushed for a career-high 421 yards on his way to his only Pro Bowl appearance.
Things haven't been quite as good since, although he did improve his accuracy in 2020, completing 67 percent of his passes.
Head coach Sean McDermott will try to unlock the quarterback's talent that was on display entering the NFL, potentially getting a steal in free agency.
The Bills are set with Josh Allen as their starting quarterback. Jake Fromm and Webb Davis were their backups prior to Trubisky's agreement.
Trubisky can compete to be the No. 2 quarterback during training camp and the preseason. He's got similar athletic traits to Allen, particularly with his ability to move out of the pocket, so Buffalo is as good a landing spot for the 26-year-old to play in 2021.