5. Alex Smith, QB (2013-17)
It's too bad for Alex Smith that things worked out the way they did. He helped bring the franchise back from its low point in 2012. With Smith as the signal-caller, KC played in five playoff games, but only advanced once.
While he was a terrific game manager who only threw 33 interceptions over five seasons, he just didn't have that little something extra to get the team over the top. For all the positives Smith gave the Chiefs, it was evident they probably weren't going to make it to the Super Bowl with him at quarterback.
So, they drafted Patrick Mahomes in 2017. Smith remained the starter that season, and had the best season of his career. He also mentored his backup, probably knowing Mahomes was his replacement.
The Chiefs traded Smith instead of keeping him as Mahomes' backup and the Chiefs have gone to six consecutive AFC championship games since, winning four. Smith did a lot for this team, and will be remembered fondly.