So, does this list differentiate between types of BIP beyond flyball/groundball? I thought there was evidence that some pitchers (read sinkerballers) generate easier to field BIP than other pitchers? If that is the case, wouldn't this list be an indication of that skill rather than a rating of the defense behind the pitchers(hence Wang being at the top of the list while the other Yankee pitchers are near the bottom)?

So, does this list differentiate between types of BIP beyond flyball/groundball?

PMR builds in a difficulty factor based on ball location and velocity. The predicted DER is an indicator of how (relatively) easy the balls behind the pitcher are to field. Wang's predicted DER is .657 - which means that he is actually giving up balls that are relatively difficult to field, normally. Part of the reason for that is that Wang had (in 2008, anyway) a high rate of line drives in play (21.2%). Contrast that to groundballer Carmona, who had only 12.7% LDIP - and a predicted DER of .711.

-- MWE

So are Carmona and Sanchez guys likely to improve, because things may even out? Or is it a thing that says "These pitchers are similar to knuckleballers in that normal DIPS doesn't work right for them."

DER is essentially the inverse of BABIP, right? Why doen't anyone us SLIP (Slugging in play) instead?

Why doesn't anyone use SLIP (Slugging in play) instead?

SLIP doesn't really tell you anything that in-play BA doesn't. Most in-play EBH are doubles, and doubles as a percentage of hits allowed doesn't have a lot of variance between pitchers.

-- MWE

SLIP doesn't really tell you anything that in-play BA doesn't. Most in-play EBH are doubles, and doubles as a percentage of hits allowed doesn't have a lot of variance between pitchers.

OK, but what about the flip side of SLIP? Wouldn't that indicate which teams had bad outfield defense?

OK, but what about the flip side of SLIP? Wouldn't that indicate which teams had bad outfield defense?

Again, not to any great degree; the variance in doubles allowed as a function of hits in play is too small.

-- MWE

So are Carmona and Sanchez guys likely to improve, because things may even out?

Carmona had one of the highest percentage of "easy" balls in play, in part because he allowed only 12.7% LDIP. It is extremely unusual for a GB pitcher to have an expected DER which is that high - Webb's never been over .700, for example - and it sounds as though Carmona might have made some changes last year that caused balls to be hit in different locations than his fielders expected.

I'd love to see Pinto do some breakdowns by in-play ball type, like he did for Wang a year ago.

-- MWE

So is the theory, then, that when Wang pitches, the Yankees suddenly become better fielders than when Pettitte pitches? Jeter suddenly develops extra range?