The problem Rothschild discovered was evident only when Wells was pitching out of the stretch, which manager Lou Piniella tied to the ex-catcher’s struggles in 2010.
Notice that when [Wells] has his troubles, or has had his troubles, there’s a guy on base.
Let’s start by comparing Wells’ performance with runners on or the bases empty in 2009—when everything was presumably hunky-dory—to his less-than-stellar 2010. Using MLBAM Gameday data (including PITCHf/x) we’ll try to spot the difference(s) in Wells’ 2010 performance and ponder the possible ties to his mechanical issues.
I’m biased toward believing in Rothschild (notwithstanding the infamous towel drill). I expected—going in—to find something in Wells 2010 out of the stretch that wasn’t there in Wells 2009. Rothschild has quite a record&,dash;and I’m not just talking about Carlos Silva. An example of his effect on pitchers can be found in this article at Another Cubs Blog. In a nutshell, time spent with Rothschild usually means more strikeouts and fewer walks.
Back to Randy Wells.
Let’s start with the bottom line. Or lines. The rvera tables below show linear weights converted to an ERA-like number. rveraA is based on pitch-by-pitch outcomes (ball, strike, error, out, single, double, triple, home run) and adjusted for the count. rveraE is the same but, instead of actual batted ball outcomes, uses league average outcomes for line drives, ground balls and infield flies.
|rveraA||Bases Empty||Runner(s) On|
|rveraE||Bases Empty||Runner(s) On|
While Wells toughened up with runners on in 2009, he’s now prone to getting pounded out of the stretch. Piniella was right.
Where does the problem manifest itself? Balls and strikes?
|Whiff||Bases Empty||Runner(s) On|
|B:CS||Bases Empty||Runner(s) On|
Interesting splits, but nothing “new” for 2010—beyond more whiffs overall. Let’s try batted balls.
|Ground ball %||Bases Empty||Runner(s) On|
Call me crazy, but maybe he’s leaving the ball up and/or not throwing his ground ball stuff as often.
Setting aside his rarely used cutter, Wells is a four-pitch righty: fastball, sinker, change-up and slider. As with many pitchers, Wells gets most of his ground balls from one of the sinker/slider combo. His change-up is ground ball neutral and his fastball is like most four-seamers. That is, prone to be put up in the air.
|Fastball %||Bases Empty||Runner(s) On|
Despite a tendency to throw a few more fastballs with the bases empty this season, Wells is still using it at the 2009 rate with runners on.
|Sinker %||Bases Empty||Runner(s) On|
Instead of increasing sinker usage with men aboard as he did in 2009, Wells shows no split in sinker usage in 2010.
|Slider %||Bases Empty||Runner(s) On|
Wells 2010 offers fewer sliders with the bases empty and a smidge more with runners on compared to Wells 2009. He’s turned a small-ish split into a large one.
|Change-up %||Bases Empty||Runner(s) On|
Wells is throwing more change-ups in 2010 with runners on base while he had no split in change-up use in 2009.
Putting it together, Wells is leaning less on his best ground ball pitches when runners reach base. Seems backwards to me, but doesn’t seem to be the big a-ha. Pitch selection is part of the story, but the story deepens when we look at the performance metrics by pitch type. Specifically, ground ball rates.
The last row of this table is the same data shown above in a slightly different layout. BE is bases empty, MOB is men on base. Obviously, the first four rows of data here are by pitch type.
|Pitch||2009 GB% BE||2009 GB% MOB||2010 GB% BE||2010 GB% MOB|
I can imagine a situation where a mechanical flaw takes a pitcher’s stuff further up in the zone, when he may have actually found it easier to get the ball down before the problem started. Wells is not having a problem getting ground balls out of the windup, so we seemed to have found a sign of agreement with Rothschild’s diagnosis—even though we don’t know exactly what he found or what he expects it to fix.
What we just saw was, in short, a failure to improve ground ball rates out of the stretch. Wells could do it in 2009, can’t do it in 2010—except with his sinker, which not only retained its split but improved overall. He’s throwing it less often with runners on base, though.
To tighten up the link between our observations and Rothschild’s, let’s dive into the all-important issue of pitch location. My analysis is incomplete, but here’s what I have found so far, a look at the average height of pitch by base state. There is no adjustment for batter height, which may make a difference.
2009: Nothing more than two-thirds of an inch different on average, except slider which was a little more than an inch higher with bases empty.
2010: Sliders have a larger split (nearly four inches) and sinkers are still within an inch, but on the right side of our splits (lower with men on base). More importantly, change-ups (3.8) and fastballs (2.7) are now higher when men are on base. That’s the “wrong” way, and fits the theory.
As I said these results are incomplete, but they are also inconsistent. The slider’s improved height split does not correspond with the drop in ground balls with men on base. The sinker is better in both (trivially so in height), and the all important fastballs and change-ups line-up with our expectation—being left up with men on base, resulting in fewer ground balls.
But it can’t be all about the raw height of the pitch. If it were, the amazing split in fastball ground ball rates from 2009 would be expected to show up in average pitch height. Perhaps a batter height adjustment, and analysis of the full distribution, are in order.
So, no firm conclusion, but I do have a strong feeling that Rothschild’s adjustment will get Wells back on the ground ball track with men on base.
References & Resources
PITCHf/x data from MLBAM and Sportvision. Pitch classifications by the author. Batted ball data from MLBAM.