1. Marty Schottenheimer - 47-33, two playoff appearances
Sure, Marty Schottenheimer has a bad reputation for blowing games in the playoffs and that is ultimately what led to him getting the can from the Chargers after the 2006 season. That does not change the fact that it was a mistake to let him go after the best season in franchise history.
The 2006 Chargers were special. For many younger fans, that was the team that sparked the love for Chargers football and has made us all sit through the pain since. There was so much talent on that team on both sides of the ball and it legitimately has to be considered one of the best NFL teams to not win the Super Bowl.
And it is a real shame too because if Marty McCree just held onto the football or Nate Kaeding just made a field goal then Schottenheimer's legacy would be completely different. He may have been the coach to bring a Super Bowl to the Chargers and would have coached another 5+ years.
The whole trajectory of the franchise would have been different. It really is one of the most unfortunate what-ifs in football history as Schottenheimer was undoubtedly the best coach the Chargers had since Don Coryell.