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Can Trevor Rosenthal command his fastball?

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Location, location, location.

MLB: Atlanta Braves at Washington Nationals Geoff Burke-USA TODAY Sports

Trevor Rosenthal was quite the bullpen nomad in 2019, never hanging around long before he was off to his next destination. And with good reason. Let’s review his transaction log.

11/3/18 - Signed with the Washington Nationals on a one-year deal.

4/26/19 - Landed on the IL with a viral illness.

5/11/19 - Began a rehab assignment in Double-A.

6/8/19 - Activated from the IL.

6/23/19 - Released by the Nationals.

6/27/19 - Signed with the Detroit Tigers on a minor league contract, reported to Triple-A.

7/15/19 - Contract purchased by the Tigers.

8/7/19 - Designated for assignment by the Tigers.

8/19/19 - Signed with the New York Yankees on a minor league contract, reported to Triple-A.

11/4/19 - Granted free agency.

That’s an insane 366 days.

We’ve been over what happened last year in this space, but it was so shocking that it bears revisiting. Rosenthal’s 2019 qualifies as nightmare fuel for any reliever returning from an extended injury. He didn’t record his first out of the year until his fifth appearance for the Nationals. That was 10 consecutive batters that reached base to open hte season against Rosenthal. Seven of those batters scored. It was reliever carnage. He never recovered.


The Royals signed Rosenthal to a minor league contract in December. If he makes the big league squad, he will earn $2 million, with an additional $2.25 million available to him in performance bonuses. He made his spring training debut on Friday, and it was a carbon copy of his premiere spring outing with the Nationals last spring. Three batters, three outs with a pair of whiffs. He reached 98 mph on the stadium radar. He looked good.

Through the course of his career, Rosenthal has relied primarily on a fastball that can hit triple-digits (duh), while mostly complimenting it with a changeup. Historically, the heater was thrown around three-quarters of the time with the change being offered at a rate close to 20 percent. In the last couple of years prior to his Tommy John surgery, Rosenthal started mixing a slider in a little more. In 2017, he threw more sliders than changeups for the first time in his major league career. The slider is a weapon.

Trevor Rosenthal pitches

Year FB% FB BA FB SLG CH % CH BA CH SLG SL % SL BA SL SLG
Year FB% FB BA FB SLG CH % CH BA CH SLG SL % SL BA SL SLG
2015 74.4% .275 .357 13.8% .140 .158 6.1% .158 .158
2016 78.0% .312 .394 13.8% .158 .273 7.8% .471 .647
2017 74.1% .271 .355 12.5% .135 .216 13.2% .094 .094
2019 69.9% .241 .276 3.5% .500 .500 24.4% .143 .143

Remember, we are referencing some small sample sizes when it comes to the results on the slider prior to 2017 (and the change from last season which almost entirely feel out of favor). In fact, so rarely did he offer the change that just two were put in play against him in 2019. Obviously, one went for a single. Such is the danger of analyzing relievers.

The point of the above table is more to illustrate his stuff is good. At that velocity, how could it not? Like any successful pitcher, the secondary offerings will play off the heat. Rosenthal uses his arsenal the way we would expect a right-handed flamethrower. Open with the fastball and go from there. The change was deployed mostly against left-handed batters. The slider evolved as a way to attack the hitters from the right side. But we shouldn’t ignore the near total abandonment of the change last year. Did he lose confidence in that pitch? Or, returning from surgery, was he not comfortable throwing it as frequently as he had in the past? According to Baseball Savant, Rosenthal didn’t throw his change once after April.

The concern, as with any survivor of Tommy John, is the command. Rosenthal has gone through periods where he had difficulty finding the strike zone even before his injury. He showed no sign of being able to locate post-injury.

Trevor Rosenthal Walks

Year BB/9 BB% LOB%
Year BB/9 BB% LOB%
2012 2.78 7.8% 78.1%
2013 2.39 6.4% 76.7%
2014 5.37 13.6% 77.8
2015 3.28 8.7% 85.9%
2016 6.47 14.7% 76.5%
2017 3.78 9.9% 71.2%
2019 15.26 30.6% 41.5%

My god. There were years where Rosenthal had solid command and years where the command deserted him frequently enough that he failed to keep his walk rate under ten percent. While his strike-throwing ability fluctuated from year to year, his strand rate was usually fairly solid—right around the league average of 75 percent. This would seem obvious, given we are discussing a pitcher, but this is extremely the case for Rosenthal: His overall performance depends on his ability to locate.

His 2019 season was an exercise in the extreme. No matter where he was pitching, he couldn’t find the strike zone. And his inability to prevent those runners from scoring was basically nonexistent.

Trevor Rosenthal 2019

Team IP BB/9 BB%
Team IP BB/9 BB%
Washington 6.1 21.32 34.9%
Washington (AA) 9.1 6.75 14.9%
Detroit 9.0 11.0 26.2%
Detroit (AAA) 5.1 10.13 19.4%
New York (AAA) 0.1 81.0 60.0%

To be fair, his final appearance in 2019 was for the Yankees Triple-A club. Rosenthal faced five batters and walked three. He hit another. And got one out. It just didn’t matter where he pitched. He couldn't get anyone out. In the majors last year, he pitched just two clean innings (outings where he faced three batters and got all three out.) On the other hand, he had five appearances where he failed to retire a single batter.

Earlier this spring, he spoke with Lynn Worthy about those struggles and his attempt to figure out what exactly went wrong.

“I really think there wasn’t one thing, because I tried throughout the process, obviously, to tweak one thing here and there and nothing seemed to really click right away. So I think it was a combination of all those things, some mechanics, the repetition of being built up and conditioned. Then the confidence in the mental side too, that continued to escalate.”

Confidence can be complicated. It can be doubly tricky when trying to comeback from an elbow reconstruction. And if the mechanics are out of whack, the pitcher could be headed toward another injury. It’s a cartoon snowball rolling down a massive hill, picking up speed and size and it tumbles toward disaster. The whole season was a lost exercise.

But now Rosenthal, a Lee’s Summit native, is pitching at home. He’s reunited with his manager from his best days in St. Louis. While it’s entirely possible the command never returns, this is an inexpensive one-year deal for a piece of the bullpen where the Royals desperately needed an upgrade. It doesn’t hurt to find out if, in a friendly environment, Rosenthal can find his mechanics, rediscover his confidence and put together a solid season in some high-leverage innings.

This is obvious analysis, but given the disaster we saw last summer, it needs to be underscored: Watch the command of the fastball. If he misses, it’s either up and in to right-handed batters or low and away. That’s the way he’s pitched historically. However last year, he missed big time in those spots.

Baseball Savant

According to Statcast, 55 plate appearances against Rosenthal ended on a fastball last year. Only 29 of those were put in play or were strikeouts. He issued a ton of walks off that heater. Again, it seems obvious. Rosenthal starts off with a fastball around 85 percent of the time. When he falls behind, his fastball usage moves to close to 88 percent. The slider and change appear when he’s ahead in the count. If he falls behind with an early fastball and sticks with that pitch, but he can’t command it... It’s not going to end well.

Barring disaster (like what we saw last year), Rosenthal will make this team out of Arizona. Can he fix his mechanics? Can he regain his confidence? How valuable he will be to the bullpen and the situations he’s used in will be entirely up to his ability to command.