Thanks to Geoff Baker for a mention of PMR in his article on defense:

Dewan introduced a well-known Plus/Minus system a few years back, then used it as the main component of his new DRS metric. But there are other top systems, like Mitchel Lichtman’s Ultimate Zone Rating (UZR) or David Pinto’s Probabilistic Model of Range (PMR), that intelligent baseball minds swear are just as good or superior.

“I like to look at all of them,” said Tony Blengino, a special assistant to Mariners general manager Jack Zduriencik, who oversees the team’s new stats branch. “It’s kind of an emerging frontier of statistical analysis, and I think they all bring something to the table. More often than not they point in similar directions. Every now and then, they don’t. But I think there’s progress being made in the fielding analysis. I think they all have something to say.”