4. Drew Brees
This is a really interesting thought process and that is why Drew Brees checks in as the fourth player to be included in this list. Brees put together one of the best careers in NFL history away from the Chargers and he is a no-doubt first-ballot Hall of Famer. However, it also isn't like the Chargers were left with a terrible quarterback, either.
If the Chargers would have never given up on Brees then we never would have seen Philip Rivers in the powder blue. Rivers is many fans' favorite player of all time and those fans likely would not have changed anything about how the situation transpired.
Plus, it is worth considering whether or not Brees could have had the same career or even been as good as Rivers if he stayed with the Chargers. Brees got to play for one of the best offensive minds in football history and didn't have to play behind one of the worst offensive lines in the sport year after year.
That is a question we will never know the answer to but we do know that Brees at least had a better career than Rivers. Brees captured one Super Bowl ring and bested Rivers in every all-time passing metric. Again, not totally Rivers fault, but every unbiased NFL fan would give Brees the better NFL career.
And while it ended up working out for the Chargers since Rivers was so good, there is a world in which Rivers didn't work out. In that case, the team's decision to let Brees walk because of injury concerns would be cited as one of the worst gaffes in NFL history.