No pitcher who took the mound for at least 50 innings in 2019 threw their four-seam fastball more than Tampa Bay Rays reliever Colin Poche. Utilizing the pitch just over 88% of the time, it went far beyond the league average four-seamer deployment rate of 37.7%. As part of 2019’s strongest bullpen, the 25-year-old Poche produced 0.6 WAR with a 3.79 K/BB rate, which was juxtaposed by his 4.70 ERA (and 4.08 FIP).

There are a few pitchers who are able to live and die by their four-seamer. The question isn’t whether Poche should continue to throw his four-seam fastball roughly nine out of every 10 pitches he throws; it’s whether he actually needs to throw it that much?

Last year, Eric Longenhagen and Kiley McDaniel put a 70 FV on Poche’s four-seamer, noting in their write up last year:

Essentially, Poche has an average fastball with three separate characteristics that make it play up. Big league hitters may be less vulnerable to one or more of these characteristics, but if not, Poche’s fastball is going to play like a 7 or 8.

He throws his fastball with almost pure backspin, which creates 99%+ spin efficiency. Under these conditions, Poche (who led the league in FA-Z, min 50 IP) is able to induce a lot of rise on his fastball, or rather, the pitch drops much less than a typical four-seamer. This is advantageous because he lives high in the zone. Hitters who try to square up the elevated four-seamer may end up swinging under the pitch because they expect it to drop more, but in Poche’s case, Mangus Force keeps the pitch up longer than anticipated. That could at least partially explain how Poche was able to produce his 34.8% strikeout rate despite his elevated ERA.

So how did Poche stack up performance-wise compared to other pitchers who used their four-seamer almost excessively? Below are the 10 pitchers who threw this variety of fastball the most in 2019, along with their pitch values and overall FIP:

Poche threw the fewest innings of the group, had a slightly better than average FIP, and was deemed to have the most effective fastball of the group. Overall, the results are varied with a couple of exceptions, one of whom is fellow southpaw Josh Hader.

Hader and Poche both do an excellent job “hiding” their fastballs (last summer, Travis Sawchik wrote an excellent rundown of Hader’s four-seamer), which could be another facet of Poche’s skill set that allowed him to throw so many four-seamers. The idea is to keep the ball out of the hitter’s field of vision until the last possible moment, thereby giving them that much less time to identify the pitch. Hader accomplished this by turning his trunk away from the hitter as he winds up, which prevents the hitter from tracking the ball until its essentially out of his hand. As for Poche, Eric and Kiley noted, “Scouts and colleagues have asserted that Poche hides the ball well, only showing it to hitters when it suddenly appears out from behind his head. Poche also generates elite down-mound extension…”

Poche presents a predictable look (fastball high in the zone), which has resulted in a below-average ERA. And yet he boasts a high strikeout rate. Let’s look at his metrics under certain counts. The chart below identifies a clear deviation of performance between two groups of counts.

Overall wOBA by count Count FF Usage wOBA 0-2/1-2/2-0/2-2 90.0% .182 All other counts 92.3% .480

Once Poche gets two strikes on the hitter, the odds of their success fall off a cliff. That’s not necessarily an anomaly league-wide; using a four-seam fastball in a two-strike situation yields a .260 wOBA compared to a .467 in all other counts. Unsurprisingly, Poche is much more successful in the former situation.

Since it appears that his four-seam fastball isn’t getting the job done in the majority of counts (and may turn into a home run liability), Poche ought to consider incorporating another pitch into the mix to become more effective. Poche’s barely-used secondary pitch, his slider, might take some of the pressure off the four-seamer and help regulate its use. Eric and Kiley graded Poche’s slider as a 55 FV. Thrown more like a slurve than a traditional slider, he gets some nice sweeping action on the pitch, which dives away from left-handed hitter’s bats and has the ability to jam righties:

Last year, his slider held hitters to a .124 wOBA, though its usage played a role. Since it was a rarity and thrown almost 10 MPH slower than his four-seamer, its effectiveness was likely more a by-product of scarcity. However, Poche has the potential to continue to stymie hitters for a few reasons.

For one, under their current design, the pitches can tunnel pretty well as evidenced by the overlay below, which uses the previous slider example matched with his fastball:

The release point of both pitches is essentially the same vertically and extension-wise, with the slider being released a tad wider horizontally. Here’s a demonstration of Poche’s typical four-seamer and slider design and shape:

In terms of design, the four-seamer and slider have about a 60-degree axis contrast. When paired, the slider’s tendency will be to cut down and away at something of a 45-degree angle off the fastball. That puts hitters in a situation such that by the time each pitch breaks past the commit point, expecting one or the other may cause additional groundball contact (off the slider, expecting a fastball), or fly balls that stay in the park (off the fastball, expecting a slider).

Should Poche continue to attack hitters with so many fastballs? We saw from the fastball usage chart that of the few pitchers who threw their four-seamer at least 75% of the time, only Hader and Green seemed to be successful doing so. Both pitchers have a good secondary pitch (the slider), which arguably could contribute to their four-seamers being so good. Poche clearly has a good fastball, but if he wants to develop into one of the better relievers in baseball, he’s going to have to use his slider more. It pairs well with his fastball and could serve him well in the counts where Poche seems to struggle. His four-seamer can still be the out pitch it was in 2019, but incorporating his slider into the mix (mainly earlier in counts) will give hitters something more to think about and make them less likely to force Poche to throw strikes where they can sit on his fastball.