Breaking Down The AL Aces

In the American League playoffs, all four teams have a lefty as their ace — CC Sabathia, Francisco Liriano, Cliff Lee and David Price — and using Pitch f/x, we can isolate data on one pitch that makes these southpaws so successful. Let’s start with Sabathia, who is relying on a new weapon this year.

Sabathia’s sinker

This year, Sabathia posted his lowest strikeout rate (7.46) and highest walk rate (2.80) since 2005. Those are still good numbers, but not the great levels he posted from 2006 to 2009. Sabathia has made up for it, though, by posting a 50.7 percent ground ball rate, the best of his career.

Sabathia’s Pitch f/x numbers can actually give us some insight into this change. Between 2007 and 2009 (the years covered by the Pitch f/x data), he threw his sinker just 9 percent of the time, but in 2010 he threw it more than 17 percent of the time. This came mostly at the expense of his four-seam fastball, which gets more strikeouts but fewer ground balls than the two-seam variety.

Here are the locations of all of Sabathia’s sinkers put in play coded for either grounder or non-grounder.

Against right-handed hitters, when the pitch is either low or away, it gets a high number of grounders. When he leaves it up and in or in the heart of the plate, righties can get the pitch in the air. Against lefties it is much tougher, and almost all balls in play off the sinker were grounders.

Liriano’s slider

Liriano has recaptured his pre-Tommy John magic and is pitching like it’s 2006 again. His 3.07 xFIP is the best in the American League, and nearly equal to Roy Halladay‘s MLB-best 2.99 mark. Along with Jon Lester, he is the only starting pitcher to strike out more than a batter per inning while also getting more than 50 percent of their balls in play on the ground — the holy grail of strikeouts and grounders.

A huge key has been his amazing slider, which he is throwing more this year (34 percent of the time). Correspondingly, his fastball percentage has dropped; it is now below 50 percent, putting him in the bottom 10 among starting pitchers in fastball frequency. Sliders are typically thrown more often to same-handed batters, but Liriano’s is so good he can still throw it against right-handed hitters 30 percent of the time. When he does throw it, he gets an extraordinary 22 percent swinging strike rate, compared to just 11 percent for the average lefty’s slider to a righty. Here is how Liriano’s slider’s swinging strike rate varies by the pitch’s horizontal location compared to the average; shaded regions are standard errors of the estimate.

He can really handcuff righties with inside sliders. The amazing thing is that Liriano throws the pitch 65 percent of the time with two strikes, so even though it’s a predictable pitch in certain situations, hitters still can’t touch it.

Price’s fastball

Price throws a ton of fastballs. His reliance on the pitch — throwing it 74 percent of the time — is second only to Justin Masterson‘s 78 percent among qualified starters. How can Price get away with throwing his fastball so often? Because it averages 94.5 mph; only Ubaldo Jimenez, Justin Verlander and Josh Johnson throw harder fastballs. As we all know, there is typically a positive relationship between fastball velocity and fastball success.

Below is a two-paneled graph that shows a comparison of the velocity of Price’s fastballs to league average, and second, the average number of swinging strikes per pitch on fastballs based on their speed for Price and for all fastballs.

Price throws his fastball nearly 5 mph faster than average — and he rarely throws a fastball slower than about 90 mph, roughly the league-average fastball speed. Looking below this, you can see that Price’s success is above and beyond the speed on his fastball. Even though he throws his fastball very often, batters have a hard time making contact with it, even compared with fastballs of the same speed. There may be something deceptive about his delivery or life on the pitch that makes it harder to pick up coming out of his hand.

Lee’s command

Lee has been throwing his fastball less often in recent years — as he throws his cutter more often — but it is still his best pitch. By FanGraphs’ pitch valuation system, it was the second-best fastball in the game, and over the past three years has been far and away the best.

This value comes from Lee’s amazing ability to command his fastball. His pitches are in the zone more often than anyone else’s, and he starts at-bats with a strike 70 percent of the time, again tops in the league. Here is a plot that shows the density of his fastballs in two inch by two inch squares, with darker color indicating more pitches in that area.

Lee is able to get his fastball in the strike zone frequently. There is remarkably little spillover out of the zone. Beyond that, he also does a good job keeping his pitches on the outer half of the plate. The result of that per-pitch command is Lee’s 0.79 walk rate. The last starter to post a BB/9 below one over a whole year was Carlos Silva in 2005; that year Silva had a 3.39 K/9, this year Lee has a 7.76. Lee combines his historically low walk rate with a respectable strikeout rate, and the result is dominance.

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Dave Allen's other baseball work can be found at Baseball Analysts.

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