From the Handbook: Defensive Statistics

This section of the Bill James Handbook has changed considerably over the years as defensive metrics have been devised, tested and improved.

The Twins player I was most interested in checking out here is Jorge Polanco, the regular shortstop who I believe is stretched at the position.

What these stats say is: He's not great, but he gets the job done.

He's at zero in "bases saved" and -1 in "runs saved," which adds up, essentially, to: He's an average shortstop. Which, if he's capable of being a productive middle-of-the-order bat -- and he hit third regularly down the stretch -- is quite acceptable.

It's worth noting, however, that 14 of the 24 shortstops listed as "regulars" at the position were better in the metrics. He's average compared to the entire set of shortstop innings, but less adept than most the guys who play most of the innings. As one might imagine for a key defensive position, the scrubs bring the average down -- and Polanco is good enough to be better than them.

Eduardo Escobar, in about an eighth of Polancos innings at short, is -2 in runs saved, and Ehrie Adrianza is +1 in about a quarter of Polanco's innings at short. That Adrianza is the best of the trio with the glove sounds right. I'm not convinced that Polanco's better than Escobar, but I'm not sure the difference matters much in either direction.