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Trevor Rosenthal and a look at pitch usage, sequencing, and location

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In the first half of 2014, Rosenthal went first-pitch fastball 85.96% of the time. Will he make an adjustment in 2015 and beyond?

Scott Rovak-USA TODAY Sports

It was an interesting year for Cardinals closer Trevor Rosenthal. On the surface, it looks like a solid season as he posted a 3.20 ERA (2.99 FIP) and racked up 45 saves (in 51 chances, 88.2%), but upon further review, his fWAR dropped to 1.0 (from 2.2), his strikeout rate dropped to 28.3% (from 34.7%), and his walk rate ballooned to 13.6% (from 6.4%). After what we saw in 2013 (especially the playoffs), we probably set too lofty of expectations for the 24-year-old closer, but at the same time, given a repertoire that includes an electric fastball and a devastating changeup, it wasn't unreasonable to expect a season better than the one Rosenthal had in 2014.

I worded it poorly on Twitter, but the main thought process behind this post was to collect as much information as possible on pitch sequencing and location in a pitcher with a "limited use" of his repertoire. I chose the term "limited use" because while Rosenthal has three potentially "plus" pitches, he really only uses two—his fastball and his changeup—and he throws his fastball ~4.5 times more often than his changeup. Before getting into sequencing, let's briefly look at Rosenthal's pitch usage (and some other data) from March 31st through July 11th (pre-All-Star break):

Basic pitch data from March 31st through July 11th:

Pitch Type Frequency Velocity Dragless H. Movement Vertical Release
Fourseamer 77.38% 97.51 MPH -2.81 inches 6.28 feet
Changeup 17.48% 87.28 MPH -9.40 inches 6.17 feet
Slider 1.67% 87.77 MPH 6.81 inches 6.25 feet
Curveball 3.47% 81.14 MPH 6.82 inches 6.25 feet

Disclaimer: For the sake of time (this portion took over five hours), I was only able to collect data through July 11th. If there is enough interest in the information provided in this post, I will be more than happy to also look at the second half of Rosenthal's 2014 sometime in February.

Fastballs, fastballs, and more fastballs

As you can see from the table above, overall, Rosenthal went with his fastball 77.38% of the time. Using BrooksBaseball's handy game log feature, I documented 171 at bats from the first half of the 2014 season. To qualify for consideration, the at bat could not be a sacrifice bunt, and it had to last at least two pitches (meaning I excluded all one-pitch ABs). Well, Rosenthal went with a first-pitch fastball 85.96% (147/171) of the time.

In fact, in 68 at bats (39.8%), the only pitch Rosenthal threw to the opposing hitter was a fastball. In those ABs where Rosenthal went strictly fastball, opponents slashed .226/.382/.302. While he held hitters "in check" in terms of batting average and slugging percentage, a .382 on-base percentage is less than ideal, especially for a closer who is often in high-leverage situations.

Of note, at one point (spanning over two outings: 4/28/14 and 5/4/14), Rosenthal threw 36 fastballs in a row. With a changeup as good as the one he possesses, this should never happen. I'm not sure who is to blame most on this matter (Rosenthal, Yadi, or Lilliquist), but let's hope we don't see it ever again.

First-pitch location

Inside Middle Outside
26.9% 10.5% 62.6%

As already mentioned, Rosenthal went first-pitch fastball ~86% of the time. Thus, opposing hitters had a pretty good idea of what to expect on the first pitch upon entering the box. Not only pitch type, but the hitter also had a two-thirds chance of guessing the correct location of the first pitch as Rosenthal went to the outside portion of the zone 62.6% of the time.

Having a decent idea of the pitch type and location makes hitting substantially easier, especially for a big-leaguer. Well, in 29 plate appearances (small sample size alert) in 2014, hitters slashed .519/.500.778 on the first pitch. With a fastball that averages nearly 98 MPH, I think it would be prudent for Rosenthal to start more hitters off with pitches on the inside portion of the zone because 26.9% simply is not enough.

All about the changeups

Rosenthal went changeup with his first pitch in 13 at bats (again, SSS alert). Opponents went hitless in those 13 at bats and struck out six times (for a fascist strikeout rate of 46.2%). With results such as these, I think Rosenthal should take his chances at increasing the sample size and going first-pitch changeup more often in the future.

Also, Craig Edwards posed an interesting response to me on Twitter that I felt necessary to address: "I'd be curious how [Rosenthal] did when he threw two offspeed pitches in a row." Rosenthal went with back-to-back changeups in 25 plate appearances (20 ABs) and produced a minuscule slash line of .100/.280/.150. Thus, the changeup has been an extremely useful pitch for Rosenthal, and I would hope he looks to it more often going forward.

Three-pitch sequences to end strikeouts

Of the 56 strikeouts during this time span, fastball-fastball-fastball closed out 18 of them (32.1%). Rosenthal's next favorite three-pitch sequence was fastball-fastball-changeup, and it netted him 12 strikeouts (21.4%). In 31 of the 56 strikeouts (55.4%), Rosenthal threw at least one changeup during the last three pitches (with changeup-changeup-fastball being his next most-used sequence).

Bottom line

While Rosenthal's fastball is one of the most electric pitches in baseball, it might be beneficial for him to increase his changeup use in the future, especially on the first pitch. Also, his changeup is so good that he really shouldn't shy away from throwing two of them in a row, either. The mere threat of a ~100 MPH fastball does a pretty good job at keeping hitters from sitting on back-to-back changeups.

Credit to BrooksBaseball for the data used to create this post.