Geno Smith
Smith had one of the most astonishing career revivals we’ve ever seen. The Jets made him their starter after he joined in 2013 but he lost his job. There was that shambolic incident with IK Enemkpali that left Smith with a fractured jaw. Smith floated around as a backup for most of the next decade.
When Seattle traded Russell Wilson to the Broncos, it left them with Smith and Drew Lock. Most people thought this was one of the weakest quarterback rooms ever. But then Pete Carroll showed his faith and transformed Smith into the Comeback Player of the Year in an incredible story (via Sporting News).