The Minnesota Twins bullpen was the dominant topic yesterday for...various reasons. It looks like it will remain a dominant topic as we head toward the July trade deadline. This blog series will be all about the Twins bullpen, but won't be concerned with internal or external additions. I wanted to take a look at how the coaching staff is tweaking the pitch selection of the current Twins relievers, and how that compares to the usage across their careers. I won’t pretend to know the reasons why pitch selection is changing, but it’s interesting to see the trends with a third-ish of the season under the belt.

Disclaimer: I am by no means a pitching analyst, and I have just started to dive into the world of Baseball Savant. I highly recommend you try it out, too. You'll probably find some things I am missing.

Taylor Rogers

No need to introduce this guy. Taylor Rogers has become a relief ace after years as a marginal starting pitching prospect, followed by some time as a lefty specialist. The pitch percentage by season chart shows a major clue to how his 2018 breakout began, and that is the usage of his slider.

Slider – “The Rog”

"The Rog" (the new nickname I have just bestowed for the slider) is the only pitch that Rogers has thrown at an increased rate in 2019. It jumped from 13.1% of his pitches thrown last year to 50.3% in 2019.It's a large key to his success against right-handed hitters, as he's able to paint both sides of the plate with superior break.

The results have not been quite as dominant as it was in 2018, but "The Rog" still holds opposing batters to a .244 BA and a .333 SLG (last year was .122 BA with a .195 SLG). For some context, he's thrown the slider 315 times since debuting in 2018, and given up a total of 4 extra base hits.

I’m confident the slider will continue to be filthy, as the spin has increased and exit velocity has decreased to 85.3 MPH from 87 MPH last season.

Curveball

The other obvious change in Rogers' repertoire is the decrease of his curveball. The fact that his curve has become a rarity is far more surprising to me than the increased use of his slider. Rogers threw a curve for 33.4% of his pitches in 2018, but only 1.8% so far in 2019. 1.8% translates to 7 whole pitches in 2019.

I'm not quite sure why Rogers isn't throwing his curve, because it was wildly effective last year. Rogers threw curveballs 316 times in 2018, allowing just 1 extra base hit with a .121 BA and .195 SLG. The spin on his curve was in the 89th percentile in 2018, and the average exit velocity was a paltry 82.7 MPH.

The spin has remained above 2700 in 7 tries this season. If he threw it more, it would warrant a nickname (a la “The Rog”). Jeremy Heffner and Wes Johnson must have their reasons. Maybe Statcast is classifying some sliders as curves. Maybe po-tay-to is po-tah-to?

Sinker

Statcast classifies Rogers’ fastball as a sinker. Sinkers averaging 94.2 MPH are usually quite filthy. It’s trending near his career average in terms of percentage of pitches thrown, but has been dethroned as his favorite pitch due the success of his slider. Regardless, the sinker is a key to establish his breaking balls and it’s going to appear in almost every plate appearance.

Rogers’ sinker has been more effective in 2019, nearly matching the performance of his slider this season. It’s always nice when average velocity increases on non-breaking pitches, and Rogers’ sinker has increased by 0.7 MPH from 2018. That seems to be a common trend across Wes Johnson’s pupils.

Four-Seamer

Rogers has thrown a four-seam fastball once this season. It deserves one sentence.

It nearly hit Gordon Beckham in 0-2 count with the bases loaded.

Overall Takeaway

Rogers has continued his dominance with breaking balls, but the pitch selection has shifted to favor his slider over his curveball. The slider hasn’t been quite as dominant as 2018, but improvements to the spin and exit velocity suggest that it’s a pitch worth throwing more than he did last year. That doesn’t quite explain the severe drop-off in curveballs thrown, maybe there’s an explanation that can’t be defined by Statcast. Regardless of this shift, he's still the ace of the bullpen.