*Note: This article has been updated. The previous image of Kershaw's release point was horizontal instead of vertical. This error has since been amended.

2018 is a pivotal year for Ryan Pressly. The Twins originally acquired Pressly from Boston in the 2012 Rule 5 draft. In five season in Minnesota, Pressly has oscillated between very good (2016 version), and so-so, (2017 version). With the front office adding significant major league talent this off-season, and a chunk of organizational relief talent in the high minors (Curtiss, Reed etc.), Pressly is entering a crucial season. He is out of minor league options. For a Twins team hoping to challenge for the AL Central, a poor April-June may mean the end of his tenure with the team.

On paper, Ryan Pressly is everything the Twins want to help anchor a bullpen which has lacked dominant arms in recent years. In January, Pressly agreed to a $1.6 million contract with the Twins for 2018, avoiding arbitration. Stuff-wise, Pressly is the kind of arm the Twins have needed to stick at the major league level. He can throw five pitches (fourseam fastball, cutter, slider, curve, and sinker) and has well-above average velocity (his fastball averaged 96mph in 2017). Pressly also generates a ton of swings and misses, with a 12.4% SwStr% (swinging strike %). For context, this was 38^th in MLB for relievers who threw at least 60 innings, sandwiched right around Brad Hand and Bryan Shaw. So why hasn’t Pressly managed to produce more consistently excellent results, given his impressive arsenal?

Variable Release Points

I’m about to do something extremely unfair to Ryan Pressly; compare him to Clayton Kershaw. That’s not really reasonable. Kershaw is perhaps, the greatest pitcher of his generation, a starter, and left-handed. Pressly is none of those things. The comparison is useful however. In the table below, you’ll see Kershaw’s vertical release points for all his pitches charted throughout the 2017 season. Notice the consistency in release points for his pitches (how clustered together they are). The result of this is all his pitches are coming at hitters from an extremely similar height, increasing the likelihood of deceiving the hitter. Pitchers typically go through subtle variations in their release points throughout the season. When Kershaw’s vertical release dips or increases in one pitch, the rest follow suit.

By contrast, Pressly has wide fluctuations in his vertical release, both throughout the season, and in between his pitches. There are two months’ worth noting in his 2017 season, May, and August. In May, there was a much greater range in the vertical release points of Pressly’s fastball and slider (his primary two pitches). In August he brought those two release points (although lower) much closer together. Pressly managed an ERA of 11.00 in May with a .324 BAA, and a 1.13 ERA in August with a 0.96 BAA. When Pressly is able to release the ball from consistent vertical coordinates, regardless of the pitch, he has the velocity required to dominate opposing hitters.

Slider Command

Pressly employs both a curveball and slider as breaking pitches. 2017 saw a significant reduction in the amount Pressly used his slider (dropping from around 25% to around 18%). Both of Pressly’s breaking pitches have fairly minimal vertical break and are both above average in velocity. When throwing breaking pitches without a ton of break, command is everything. Below are two charts mapping Pressly’s slider and curveball location in 2017.

It’s immediately noticeable that Pressly leaves far too many sliders over the heart of the plate. By comparison, Pressly locates his curveball more consistently down and away to RHH (down and in to LHH). His slider command struggle is reflected in the effectiveness of both pitches in 2017. Pressly’s curveball had a .194 SLG against in 2017 (with around 21% whiffs), compared to .463 SLG for his slider (around 15% whiffs). In other words, when Pressly left his slider over the plate, the break he generates is not enough to save him, and excellent professional hitters tend to have their way with it. For one final comparison, the last chart here shows Pressly’s slider command in 2016, his best full season with the Twins. His ability to cluster slider location down in the zone is noticeable. In 2016, Pressly gave up a .375 SLG on his slider, and .089 ISO, compared with .256 ISO in 2017.

Upon looking into Pressly’s numbers more closely, there’s only one conclusion to draw, he’s never established great enough level of consistency in his mechanics throughout his tenure with the Twins. Variations in his release point and command struggles have diminished the impact of his incredible arm. If Pressly is going to stick in the Twins’ pen long term, mechanical consistency is the key lever that needs to improve to capitalize on his excellent arm