Alex Smith
Smith’s well-documented injury came in 2018 when he took a sack against the Houston Texans. Washington led the NFC East but it all went downhill from this game. Smith suffered a horrific leg break that legitimately almost killed him. An infection set in and surgeons considered amputating the limb.

The Texans won the game and a malaise set in. Colt McCoy became their starter for the rest of the season but they only won two more games. It was a shambles as they missed the playoffs. Smith was in good form before his injury but this was a disaster and they arguably haven’t recovered (via ESPN).