Originally written on Fangraphs  |  Last updated 11/17/14

Drew Pomeranz takes the mound today for the Colorado Rockies. The 23-year-old lefty came into the 2013 season with Matt Moore expectations, but so far has Jamie Moyer results. On Tuesday, he takes the bump aiming for a solid 4.0 IP against the playoff contending Atlanta Braves, and if he hopes to salvage anything from his forgettable rookie season, he will need to get his secondary pitches working for him.

Pomeranz has improved over the last two months, as his K-rate and BB-rate have both moved in the right direction:

But in order for his success to grow, Pomeranz will need to dramatically alter his approach, and that starts with his curveball.

The Colorado Rockies have had, to say the easiest of truths, a difficult go of preventing runs in 2012. They have the league’s worst ERA by 0.39 points despite having only the league’s sixth worst expected FIP at 4.26 xFIP.

The Rockies play on what amounts to Earth’s moon, so it surprises few people that they lead the league with a 14.2% HR/FB rate. But the Blue Jays have a 14.0% HR/FB rate, and their team has only a 4.55 ERA with their 4.28 xFIP. The Rockies also have a terrible 68.6% LOB rate, which puts them second-worst in the MLB, and a .321 BABIP, which puts them in the running for a legit shot at the Defense/Park-Dependent Stats Triple Crown.

Pomeranz is certainly doing his part for the DDPS Triple Crown with his 13.9% HR/FB rate and 67.7% LOB rate, but even those sins could be covered if he did not sport a pedestrian strikeout rate and a dangerous walk rate. And looking at his PITCHf/x run values, we can see his No. 2 pitch, his 77 mph curve, has earned a hefty share of the blame.

With run values of -6.9 wCU and -4.57 wCU/C it becomes apparent that something is amiss with a curve that — coming out of college — had the reputation of having great command:

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If we look at his curve locations to both hands this season, we see Pomeranz has a very acute location for success with his curve, down and in on righties and down and away on lefties:
Curveball

Essentially all the swinging strikes against his curve have come in that bottom left quadrant (from the catcher’s perspective). And since he is getting whiffs on 30% of swings against his curve, it is apparently doing the job when it is in the right place. A very, very narrow and specific “right place.”

Strange Thing: The Pomeranz curve has only allowed 7 singles, 2 doubles, 1 triple and 2 homers on 152 pitches (a mighty .079 batting average). That’s 12 hits on 152 pitches. But since it is in the zone only 40% of the time and hitters are only swinging at a pitiful 23.6% of those out-of-zone pitches, Pomeranz is throwing a lot of balls with his curve.

Adam Wainwright has one of the best curveballs in the nation. He throws his curve for a strike only 41% too — in fact, only 38% in 2012 — but hitters swing almost half the time he throws it, and they swing 41% of the time he throw it out of the zone. Granted, that is where the similarity ends. Looking at the pitches in or near the zone, Pomeranz actually reports better control. Looking at these comparative heat maps, we can see both Wainwright and Pomeranz scatter their curves with almost equal randomness — except that Wainwright throws his curve, like, every other pitch:


NOTE: This is just from 2012, dawg.

Clayton Kershaw probably makes for a more accurate proxy — or better yet, a role model — for Pomeranz. A lefty himself, Kershaw also leans heavily on his fastball and works in breaking stuff as a compliment. Pomeranz is more fastball-friendly, and Kershaw throws a nasty slider as his No. 2 pitch, but his curve also gets some of the league’s best results.

Kershaw throws his curve in the zone at 41% also, and — like Wainwright — generates more out-of-zone swings (28.3% in 2012) than Pomeranz. And his in-zone contact rate (74.1%) allows him to throw his curve for a strike with considerably more confidence.

So why is Pomeranz’s curve not working? Why does it have a ridiculous 96% contact rate in the zone? Why do hitters know to lay off when it is out of the zone? Scouts have suggested his curve is a plus, yet hitters think it’s an easy minus.

Even more troubling is that his fastballs — four-seam and two-seam — have a combined swinging-strike-per-pitch rate of 16.8% against lefties, but only 6.8% against righties. This has led in part to an increasingly worrisome 4.85 xFIP against righties despite a 3.32 xFIP against lefties. Because his fastball cannot seem to dominate righties, and his curve appears quite transparent to both hands, it seems the culprit may in fact be in part his third pitch — his changeup — which has clearly not developed to a major league level yet.

His change has a contact rate of 87.5%, and the out-of-zone swing rate is also an absurd 10.6%. If the hitters kill a pitch in the zone, and the ignore it out of the zone, it is pretty much not a worthy pitch. If Pomeranz cannot generate significant improvements in his curve or changeup — or find a pitch that can help him against righties in some fashion or make his curve more deceptive in some other fashion — he may find himself in the minors — or worse, as a LOOGY — sooner than anyone every expected.


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