The Stuff That Dreams Are Made Of: Aaron Thompson

Many popular opinions of pitching prospects are formed from general scouting reports. While these reports are invaluable resources, they can’t always be trusted. Hundreds of minor league hurlers are credited with “mid-90′s velocity,” but very few MLB starters actually have that grade of heat, for example. It’s incredibly frustrating to hear about a pitcher with “a mid-90′s heater and plus curve,” only to have him come up to the big leagues and show a fastball that averages 90.5 mph and a slider.

When a pitcher come up to the majors, we can finally get a foolproof reading on what exactly his arsenal is comprised of, thanks to the great Pitch F/X system. In this series, I analyze just that–the “stuff” of recently-promoted MLB pitchers. Now that they’ve achieved their big league dreams and thus factor directly into the MLB picture, it’s high time that we know exactly what these guys are providing.

This time, I’m taking a look at Pirates swingman Aaron Thompson.

Aaron Thompson’s call to the majors was one of the stranger ones in 2011. After all, he had spent most of the year in Double-A, where he posted a 5.16 ERA, striking out just 51 batters in 83 2/3 innings. He then walked nearly as many batters as he struck out in a brief Triple-A run, but managed a 2.84 ERA there nonetheless, which apparently was enough to get him one start and three relief appearances for Pittsburgh down the stretch.

It should come as no surprise that they didn’t go well–he walked six and struck out only one batter in 7 2/3 innings, good for a 7.10 ERA and 8.35 FIP.

The 24-year-old southpaw throws three pitches from a clean delivery, none of which are really impressive.

His fastball doesn’t have much in the way of velocity, as he can touch 90-91 mph in relief but mainly works at 86-89, and the pitch is fairly straight. He also has an 82-86 mph slider and an 80-84 mph changeup, so the velocity on just about every pitch he throws starts with an 8.

His delivery, while mechanically sound, doesn’t create much deception, and furthermore, he doesn’t throw his pitches from the same arm slot:

It appears that Thompson uses a different arm slot for his slider than his fastball and changeup, which means hitters can probably pick it up more easily.

As one might expect, he’s not fooling anybody, as his miniscule 3.9% swinging strike rate attests. Just one of his 75 pitches that Pitch F/x classified as four-seam fastballs drew a swinging strike, and his slider was the only pitch that showed any promise in that regard (three whiffs in 32 pitches).

To his credit, Thompson does do a decent job of attacking the lower half of the zone:

His fastball (65.3%) and slider (68.8%) both ultimately went for an above-average number of strikes, but the pitches that Pitch F/X classified as two-seamers and changeups (most of which are changeups, but a few of which are fastballs) only went for strikes 34.8% of the time. You can see all of those yellow triangles outside of the zone, for example.

With none of his three offerings profiling as even average, no deception, and merely average command, it looks like Thompson is just an insurance arm. With none of his three pitches having great speed or movement separation, he just doesn’t have a dynamic enough arsenal to hold his own in the majors, and he doesn’t have enough pitchability to make up for that.

For more on the Pirates, check out Rum Bunter.

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