Donovan McNabb
Nobody will pretend that McNabb was the greatest quarterback ever. But he did a good job for the Eagles and it was a major blow when they lost him to injury in 2005. This came after their Super Bowl appearance against the Patriots. Their fans hoped that they’d push on but that’s not what happened.

We’ve seen rare exceptions with Tom Brady and Brock Purdy. But usually, a QB injury ruins a season. That’s what happened in this case because the Eagles fell apart with Mike McMahon as their starter. Meanwhile, a clutch of other players suffered injuries in a trainwreck season (via ESPN).