JABO: The Most Irreplaceable Player

We have stats to help us understand which players are least replaceable in general. But the rosters are almost set, and now we can ask a specific question. Which players are least replaceable by the personnel on the team around them, right now?

To do this, we can use the depth charts on FanGraphs, manned by the writers on staff. These oft-updated team maps dole out the playing time by keeping an eye on health and current spring training updates.

So let’s compare the position players in baseball to their backups. Because players can be listed at multiple positions, these depth charts do a decent job of looking at what might actually happen should a player go down. Take a look at the Indians, for example. Brandon Moss won’t be on the bench waiting for Carlos Santana to be hurt, but if Santana is out of the lineup, it’s most likely Moss that will step in.

We can’t use counting stats to compare the starter to the backup, that should be obvious. Since defense is still an important part of the discussion, Wins Above Replacement is a good framework for us. Let’s pro-rate everyone’s WAR to 600 plate appearances so they are on the same footing. We used decimal points with the projected WAR just because we have to — there’d be a lot of backups with zeroes otherwise.

Now all we have to do is subtract the backup’s WAR/600 from the starter’s number, and we’ll get a list of the least replaceable players in baseball. Let’s group them by the number of wins their team would lose if they had to start the backup all season.

Read the rest on Just a Bit Outside.