I won’t lie- I was a Rosenthal hater.
I used to be the world’s #1 opposer of Trevor Rosenthal as a closer. Back in the day when he had that job, it just seemed like every time he came in to pitch, he allowed a few runners on before he shut the door. He basically handed the hitters an opportunity to win the game. Whether or not the numbers support that feeling, I will get to later. And then last year happened, and I literally was going around to say “I knew this would happen, I told you so.” Coming into this year though, Rosenthal is making me choke. on my words.
Was my hatred justified?
Not at all, Rosenthal has a career ERA and whip of 2.90 and 1.30. So the numbers do not show what I was feeling as I thought they would, but what about movement on his pitches? This is where I found something. The RPM of his fastball was lower a few years ago than it is now. However, that is not what I saw when I watched him throw. I was more concerned with what I saw as a lack of control, but I could not find any data supporting it. So in short I was wrong.
— St. Louis Cardinals (@Cardinals) June 1, 2017
What happened last year?
Well outside of being hurt, he was doing way too much for his own good. When you are a starter, you need four pitches you can throw for a strike in order to survive multiple times facing a batter in a game. As a reliever, you are most likely only facing a batter once per game. Therefore, you really only need two distinct pitches to keep him guessing. In 2016, and in years past, Rosenthal had 5 pitches he tried to throw (4 seam fastball, 2 seam, curve, slider, change). For a guy that only goes about 80 innings a year, its hard to get a feel for all your pitches before your outing is over. His wide arsenal of pitches eventually caught up to him.
Here comes a more mature pitcher.
In 2017, Rosenthal has eliminated his curveball and used his two seam less. This allows him to focus on the three pitches that are nasty to begin with. If you want to know the exact RPM changes from year to year, go to baseball savant, but I do not need to see those numbers to know that Rosenthal is a much better pitcher now. His slider has more movement to it, his fastball is averaging 2mph higher to 99.1. Combine that with an average change up, and it suddenly becomes well above what you expect. Opponents have only hit 17% of his pitches to center opposed to his career average of 33%. It may not seem like much, but it paints a perfect picture combined with a lowered hard contact rate of 17.1%. It shows that hitters are not timing his pitches and making weak contact (late on fastball and early on change-up). All in all, I was wrong about Trevor Rosenthal. If he continues to pitch like this, he might pitch himself into another closer role.
Photo- Jeff Curry USA Today