July 31, 2014

Statistically Speaking: Stephen Strasburg’s Heat

The modern day version of Stephen Strasburg has been confounding. Despite fantastic stuff and most of his statistics showing an above average pitcher, there still remains a disconnect between expectations and outcome. As Strasburg continues to flounder in light of above average talent, there are many who point to his use of the fastball as the tipping point between his being simply a frustrating talent versus a perennial All-Star and undisputed ace. Whether it is frequency of use or the failure of a full return to pre-Tommy John surgery velocity that is the culprit is debatable, the evolution of Strasburg’s fastballs and his trust in the pitch is nonetheless an interesting development.

First, let’s take a look at Strasburg’s pitch selection over his career—post-Tommy John surgery, he has apparently scrapped the two-seam fastball (here labeled a sinker) in exchange for more offspeed pitches, including the slider, which is new to 2014.


The fourseamer is still Strasburg’s go-to weapon, but there does appear to be an initial drop in usage this season, with a return to using it nearly half of the time starting in May, again with more offspeed offerings in the form of the changeup.

How about that fastball velocity?


As many have noted over the last couple of seasons, Strasburg’s ultra elite velocity is now just…elite—the fourseamer averages right at 95 miles per hour, while the twoseamer/sinker is a little under 95, down roughly three miles per hour compared to his pre-injury days. Despite the dramatic drop, this is velocity that still has Strasburg in the top ten for National League average fastball velocities for starters. However, both of Strasburg’s fastballs have lost some of their effectiveness thus far in 2014, with the fourseamer at a 0.03 pitch value per 100 pitches and the twoseamer at -0.74 pitch value per 100 pitches, per FanGraphs. While there is a sample size component to this statistic, especially with the twoseamer, this drop from last year’s numbers—0.62 and -0.27, respectively, is potentially troubling.

In some respects, the Strasburg of recent vintage is a tale of four different fastballs—two grips, but also two speeds. Gone are the days of the pure gas that defined him in earlier days, with a line of velocity delineation being 95 miles per hour. Looking at all of Strasburg pitches thrown over the past two-plus seasons, we find 95+ miles per hour fastballs accounting for roughly 45 percent of pitches thrown in 2012 to 36 percent in 2013 and finally to 16 percent in 2014. With this in mind, let’s move forward and take a look at these fastballs in this fashion—twoseamers and fourseamers above and below 95 miles per hour—and see if this distinction provides any additional insight.

First, a look at Strasburg’s sub-95 fourseamer outcomes in 2014:


…and here, sub-95 twoseamers of 2014:


Roughly a third of each fastball are balls, with a quarter to a third are called strikes, with the remainder a mix of various types of batted balls along with some whiffs. Now, let’s take a look at 95-plus fastballs, but adding some additional data, looking at each across the 2012, 2013, and 2014 seasons, from left to right. First, fourseamers:


…and the same thing for twoseamers, from 2012, 2013, and 2014, left to right:


Reviewing the fourseamer data, it appears that Strasburg has better command of the sub-95 stuff, with fewer balls called. This comes with fewer balls in play, but slightly more hits with the lower velocity fourseamer, as well as less ability to get hitters to swing and miss. For the twoseamer data, it’s a somewhat different story. More called strikes are seen with the sub-95 heat, with a dramatic drop in called strikes across year with the 95-plus twoseamers. Interestingly, Strasburg’s sub-95 twoseamers are getting hit less and are getting more whiffs compared to the high heat, with rates similar to previous year’s 95-plus pitches. Fewer balls and fewer balls in play also make the sub-95 twoseamer on the surface a different beast altogether, and perhaps a better one, compared to the 95-plus twoseamer.

Briefly, let’s take a look at location, again comparing the sub-95 two- and four-seam fastballs of 2014 compared to 2012-2014 95-plus heat.

First the 2014 data—fourseamers are on the left and twoseamers are on the right:


…and here are fourseamer (top) and twoseamer (bottom) data for 95-plus pitches across the post-Tommy John era:



It’s a lot of data to digest, but there are some subtle differences seen. Not surprisingly, Strasburg’s command of the sub-95 stuff is a tad better than the 95-plus heat. Another trend seen is Strasburg not really using the corners of the plate with the 95-plus fastballs, appearing to almost nibble the outside corner with the twoseamer and leaving the fourseamer up in the zone and down the middle of the plate. While this is presented context free with no references to batter handedness and counts accounted for, an overarching thought looking at these heat maps is perhaps this is a ramification of overthrowing the fastball, either out of frustration or perhaps in order to ramp up the velocity to blow a guy away with strike three.

While much of these results are somewhat arcane and subtle, it does show an interesting trend with respect to the waning fastball velocities of Stephen Strasburg. Fewer high octane fastballs, a disappearance of the twoseamer in favor of a new pitch and other offspeed pitches all have the potential to account for some of the disparities between Strasburg’s stuff and his outcomes, with a return to the twoseamer and a scrapping of the slider possibly an attractive change for the better. Looking at our first graph of pitch selection, this is perhaps what we are starting to see.

While they aren’t the fastballs of old, the sub-95 twoseamers and fourseamers do have some advantages over the pure heat and could potentially help Strasburg in the long run with respect to remaining economical with his pitches and also applying a more simplified approach to getting hitters out. Strasburg remains a special talent who is in rarefied air in his ability to dominate with his fastball above all else, despite tangible velocity decreases post Tommy John surgery.


Data courtesy of Brooks Baseball and Baseball Savant.

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