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McCarron started three games in four seasons with the Bengals, all of which came at the end of the 2015 season after starter Andy Dalton broke his thumb.
McCarron was 2-1 as a starter, completing 54 of 83 passes for 554 yards with four touchdowns, no interceptions and a passer rating of 100.1.
With the Bills trading Tyrod Taylor to the Browns last week, it appears McCarron will get a chance to compete for the starting job.
His departure leaves the Bengals with Dalton and Jeff Driskel at QB.