More Wandy Rodriguez Talk: Pitching Linear Weights

Whilst in the midst of a FanGraph chat Wednesday, Dave Cameron brought up a good point about linear weights. I'll let Beyond the Box Score take it from there:

"I do think that we need to do more work on pitch type linear weights in the future. I see people quoting these as gospel, saying so and so had the best curveball in the game or what have you, and they aren't defense-independent, so I hesitate to use them in that way."

Since I had just used linear weights in discussing one Wandy Rodriguez the night before, I paid particular attention to this and the comments in the BtBS post. What do we know about linear weights? I use them from time to time, but I surely haven't made a huge deal out of his curve's linear weight dropping off a cliff. Shouldn't we be worried about that?

To answer that question, I thought we could put his numbers this season into a little context. After the jump, we'll look at what his curve looked like physically the past two seasons, how he sequenced it and where he located the pitch. Maybe then we'll be able to better understand what his linear weight means.

You may not remember, but Roy Oswalt called Wandy's curve "the best curve in baseball" last spring. Lo and behold, his curve had one of the highest linear weights according to FanGraphs in 2009, so Roy was onto something. Then, for some reason, that effectiveness ended in 2010. Did the pitch lose some of its break? Let's look to Pitch F/X to find out:

2010

2009

Not much difference there. Wandy's curve had a little less vertical drop in 2009 and a little more horizontal movement in towards a right-hander, but not by a lot. The spin rate was a little higher in 2010, which could explain why the pitch dropped more, but neither were significant enough to justify a change in the linear weight.

If the pitch itself didn't change, maybe the timing of when he threw it did. Let's look at a breakdown of the counts he threw curves on in the past two seasons:

Now we're starting to see a pattern. Wandy emphasized his curve a little more in 2010, but not by much. The real change came in when he threw it. In 2009, when the pitch had such a big linear weight, Wandy concentrated his curve in counts when he was ahead, using the hammer curve as an out pitch. His percentages didn't move much in those counts, as the curve was still his standard pitch to throw when he needed a strikeout. What changed is when he also chose to throw it.

Look at the percentages in some of the counts he was likely to get hit in. 0-0, 1-0, 2-0, they all showed an uptick in how much he used the curve. Heck, he even saw an increase in 3-1 and 3-2 curves. What that suggests is that maybe Brad Arnsberg wanted him focusing on locating the pitch instead of just throwing it for a strike to get guys out. The reliance on fastballs in hitter's counts suggests Wandy may not have had confidence always to throw his curve for a strike when he needed it. Arnsberg may have changed that as part of his "plan," which in turn could have also led to a slight uptick in Wandy's walk rate.

But, we still have to look at location. If he's throwing more pitches in hitter's counts, did he change where he threw them. For these next two charts, I looked only at right-handed batters to see if the pattern changed.

There you have it. Wandy changed not only when he was throwing the curve, but where he was throwing it. Instead of pounding right-handers in at the knees, Wandy focused on the bottom lower triangle of the strike zone. Draw a line from the lower left corner to the upper right, and basically no curves got above it. Look at how many times he threw that curve up and in last season compared to 2009. Also look how much he used the entire bottom of the strike zone as compared to the inner corner in 2009.

Now we know that Wandy used his curve more in even and hitter's counts in 2010, throwing it almost exclusively low and away. That probably led to more contact, but weaker contact, which in turn would have led to a higher ground ball rate. A higher contact rate means more hits trickling through, which will weaken his linear weight.

There's still things we don't know. We don't really know the sequencing of his pitches that led to his effectiveness. We don't know how little changes in when he threw the curve, like in his percentage dropping on 0-2 counts, affected his other pitches. What if a batter was expecting the curve 0-2 and he threw the change instead? That strikeout would raise the linear weight of the change, but it was set up by his curve being effective earlier in the count. In short, there's a lot still unknown about how good his curve was last season. What is clear is that the pitch didn't use its effectiveness. Wandy just changed how he used the pitch and still stayed successful overall. That in itself shows that he's become a pretty darned good pitcher.