What Does Drew Pomeranz Bring to the Red Sox?

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The Boston Red Sox have been busy lately acquiring relief help in Brad Ziegler and an experienced infielder for the bench. Will the team need to deal away more assets or can their ace and the new addition stabilize the rotation?  Ian York explores the repertoire of recent Boston Red Sox acquisition Drew Pomeranz to see what he offers his new team.

The Red Sox’ newest starter, Drew Pomeranz, has had a bit of an odd career to go along with his odd pitch mix. Drafted by the Cleveland Indians in 2010, he was traded to the Colorado Rockies in 2011 and debuted as a starter for the Rockies that same year, at the age of 22. Over the next three seasons, he started 30 games for the Rockies and relieved in four more, ending up with a mediocre 5.20 ERA (89 ERA+) before being traded to the Oakland Athletics. In Oakland, Pomeranz was much more successful (3.08 ERA, 125 ERA+) over two seasons, roughly equally spent in relief and as a starter. He has continued to be effective as a starter with the San Diego Padres so far in 2016, with a 2.47 ERA (159 ERA+).

In previous seasons, Pomeranz has almost entirely relied on just two pitches – four-seam fastball (“FF”, in the charts here) and curve (“CU”) – occasionally mixing in a changeup when starting games, but not in relief. It’s difficult for a starter to be effective with just two-and-a-bit pitches, and in 2016 Pomeranz has added a third pitch, a cutter, to his toolbox. We can look at his repertoire over the 2015 and 2016 seasons by game:

Several things stand out here. First, the occasional changeups (“CH”, in orange), are only present in the games he started – that is, all of the games in 2016, the first eight in 2015, and the game on 7-23-15. He throws the change almost entirely when behind in the count (about 30% of 2-0 and 3-0 pitches, compared to 6.1% on 0-1 and 0.0% on 0-2).  

Second, Pomeranz uses his curve (“CU”, in green) a lot: 30-40% of his pitches are curves, increasing to 50% when ahead in the count and lower when behind. Third, the cutter (“FC”, in gold). We can see him cautiously trying it out in his first seven games this season, and then committing to it, starting on May 18, and using it 15-20% of the time. His statistics in those games are in line with his season averages (2.90 ERA, vs. the season’s 2.47; 1.05 WHIP vs the season’s 1.06), but it seems likely that adding a fourth pitch should make his performance more sustainable.

PITCHf/x also identifies a sinker, or two-seam fastball (“FT”, in blue), but the four-seam fastball (“FF”) and two-seam smear together with no obvious separation in terms of movement or velocity; although they are shown as separate pitches in these charts, I would treat them as minor variants of the same pitch. For that matter, his changeup also smears into the fastball mix, such that Pomeranz basically throws the same pitch with a velocity anywhere between the low 80s to the low 90s, with gradually increasing movement on the slower pitches.

All four of his pitches are highly effective. Of the 96 qualifying pitchers this year, Pomeranz’s fastball ranks 10th, his cutter ranks seventh, his curve is 24th, and his changeup is first, well above the second-place Danny Salazar.

Here are what these pitches look like compared to pitches from all other left-handed pitchers who have thrown at least 50 of each type this season. In these charts, Pomeranz’ pitch’s mean horizontal and vertical movements are shown in red, with other pitchers shown in blue:

Pomeranz’s curve is dramatic, with huge vertical movement and very little horizontal movement. By comparison, his fastballs have significant, though not extraordinary, horizontal and vertical movement (though, of course, as a fastball, these pitches rise compared to the path they would follow according to gravity alone, while curves drop). And his cutter, somewhat surprisingly, has almost no movement at all compared to the path it would follow through gravity alone. However, remember that batters expect fastballs to rise naturally, so by failing to have vertical movement his cutter is deceptive.

The difference between Pomeranz’s pitches is easily seen by animating individual pitches. Here is a typical cutter, compared to a fastball, in three views, compared to the path they would take according to gravity alone (the solid line). Each dot shows the position of the pitch at 1/100 second intervals.

Note the dramatic horizontal and vertical movement of the fastball, compared to the almost complete lack of spin-induced movement of the cutter.

Here is the same cutter, compared to a typical Pomeranz curve:

This time, neither the curve nor the cutter shows significant horizontal movement, but the curve drops far below the gravity-only path.

By adding in the cutter to his pitch mix, Pomeranz can now attack batters with a vast range of pitch movements and velocities. Although it remains to be seen how well he can stand up to the innings requirement of a full-time starter, his effectiveness this season was probably not just a fluke.


Ian York uses the PITCHf/x to monitor the strike zone, highlights great performances, monitors league-wide trends and tracks the performances of some interesting young hitters.

Follow Ian on Twitter @iayork.

All data compiled from PITCHf/x and Baseball-Reference.com.

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Ian is an immunologist and virologist who lives in Atlanta with his wife and two sons. Most of his time is spent driving his kids to baseball and soccer games, during which he indoctrinates his children on the glories of Pedro Martinez, the many virtues of the Montreal Expos, and other important information.

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