https://phys.org/news/2018-07-star-players-over-rated-mlb-key.html

But does it actually measure—or even roughly estimate—player value?

Initially, Austin Brown—a Ph.D. student at the University of Northern Colorado in the department of applied statistics and research methods—was interested in figuring out the relationship between injuries, teams catching the injury bug throughout the course of the regular season and team performance. But as he worked on the topic with his adviser—Jay Schaffer, professor of applied statistics and research methods—they began to look at the relationship between individual players and team performance. "Our thinking was that a player of lesser quality is unlikely to impact overall team performance in the same way as a player of higher playing quality," he says. "And that led us to WARP."