What makes a player irreplaceable?

You don't have to look far down a college football team's roster to find the difference-maker who jumps off the page as the program's unquestioned leader, a player who not only shines from an individual standpoint but exudes a work ethic and will to win coaches use as as example for others.

We're talking about the franchise guys, starters whose teams could crumble if taken out of the lineup. He's the player first on the flight to preseason conference media days and anxious to lead the pre-game huddle on gamedays. You can't teach it and most of these talented players are blessed with it.

Here's a look at college football's 19 most irreplaceable players ahead of the 2019 season: