Trevor Rosenthal: Starting Pitcher?

#Cardinals closer Trevor Rosenthal on being named club's closer, jokes: "They don't know it, but I'm still competing for a starting spot."

— Derrick Goold (@dgoold) January 18, 2014

In my last baseball-related post on my old blog before joining Viva El Birdos, I wrote about the mystique that is Trevor Rosenthal's fastball. My conclusion? Rosenthal could go down as one of the best closers ever if he stayed in the role and was able to remain healthy. Well, The Continental posed the following questions in the comments section that have had me thinking ever since: "Don't you think limiting Rosenthal to ~75 innings a year is a waste? Is that the best way to utilize him?"

I never got around to answering his questions because I had this exact post in mind. Is ~75 innings from an arm as lethal as Rosenthal's worth it for the Cardinals? Aside from Carlos Martinez, Rosenthal likely has the most electric stuff on the staff. Returning to questions posed in the first paragraph: Would he be more valuable to the team as a starter and pitching 150+ innings a season? After some thought, I would answer this question with a resounding yes.

Well, as Derrick Goold made quite clear in the above tweet, Rosenthal was just joking (or was he?). With roughly three weeks until pitchers and catchers report, let's discuss the idea anyway. At 23 years old with a potentially crowded bullpen, I believe this spring is the perfect time to give Rosenthal a legitimate chance at cracking the starting rotation. Rosenthal is too good of a teammate to become a distraction by openly campaigning for a starting job, so I will make his case for him.

Let me be clear about one thing right away. I do not want this to be a halfhearted attempt either. Hand over the "keys" and give him every opportunity to win the spot. Start him in multiple games against quality opponents. Allow him to work his way in and out of jams. Give him extended starting pitcher innings, somewhere along the lines of Tim Hudson's 2013 Spring Training in which he pitched 30 innings. If things look good, plug him into the back of the rotation to start the season. If things look promising but the organization is unsure about his projectability over the long-haul, extend his "tryout" into the beginning of the regular season.

But could he even succeed as a starting pitcher at the major league level?

His off-season training regimen with Matt Holliday was continuously hyped up by the media after he talked about it in an interview at the Winter Warm-Up. To me, it sounds like this workout program was tailored towards developing the strength and stamina needed to be a successful starting pitcher. Let's see if it will pay immediate dividends or not. Those secondary pitches he needed to fine-tune over the off-season? Let's see just how much work he put into gaining comfort with them. We, along with everyone around the majors, know just how good his fastball is, but unlike many from around the majors, we know just how good his secondary pitches (especially his changeup) can be as well.

Here's how Rosenthal performed as a starting pitcher in the lower levels of the minors back in 2011 and 2012:

Does his performance as a starter in the lower levels of the minor leagues correlate to the performance we can expect from him at the big league level? Not really, but I provided these statistics to show he was a capable starter at some point in his professional career and that it wasn't too long ago. The fact that he averaged 5.45 innings per start despite undoubtedly being on a pitch count is a good sign as well.

His repertoire and release points

Rosenthal's go-to pitch out of the bullpen has been his electric fastball. Duh. According to his player card on BrooksBaseball.net, his fourseam fastball averaged just over 97 MPH in 2013. However, in order to pitch deep into games as a starter, Rosenthal will not be able to ramp his fastball up to 97+ MPH consistently like we saw from him out of the bullpen last season. With a fastball likely ranging in the 93-95 MPH range as a starter, he will have to prove he can be a pitcher instead of just a hard-thrower, and in my opinion, his changeup will be the kicker for initial and possibly sustained success as a starter.

Let's take a quick look at the average release points of his pitches in 2013:

As you can see, I compared the release points of his secondary pitches to that of his fastball, since it is by far his most used pitch, and subsequently the arm slot hitters will focus on most when facing him. The most glaring difference from the chart is obviously his curveball—a pitch he releases (on average) 3.89% higher than his fastball. However, this makes sense because in order for a curveball to avoid landing in the dirt on a consistent basis, the pitcher must use a higher release point. For comparison and reassurance, Adam Wainwright released his curveball 5.14% higher than his fastball in 2013.

Then why did I even show you this? The release points of his changeup and slider are less than 2% different than that of his fastball. Well, to be honest, I would like the difference in his fastball and changeup release points to be even less going forward. Let me explain why by comparing him to another young pitcher in the Cardinals rotation.

Michael Wacha was essentially a fastball-changeup pitcher for the majority of his rookie season. His changeup was nearly unhittable, leading to whiffs on nearly 40% of swings. Sure, the downward plane produced by Wacha's 6'6" frame had a lot to do with this, but I would argue that a bigger reason was the uniform release point of both pitches. On average, Wacha released his changeup just 0.3% (one-fourth of an inch) higher than his fastball. From 60 feet, six inches away (actually 5-6 feet less due to the pitcher's stride), there is no conceivable way hitters could tell the difference between these two release points. Rosenthal released his changeup 1.2 inches (5x the difference of Wacha's) lower than his fastball—a difference major league hitters (through teammate collaboration and video replay) could pick up on over the course of a game and most definitely over the course of a season.

Despite the difference in release points I just pointed out, his changeup was still nearly unhittable last season. Its horizontal movement averaged 7.39 inches—nearly half the width of home plate. Its velocity (88.15 MPH) was right at the desired 10 MPH drop-off from his fastball. It led to whiffs on 49.15% of swings. When hitters did make contact with this pitch, it wasn't solid contact considering only 13.51% of the balls in play were line drives—10% lower than any of his other pitches.

Thus, he's already got one (double) plus pitch in his fastball, and he has shown the potential of having another in his changeup. But can a two-pitch starting pitcher really succeed in the MLB? Jeff Sullivan had a nice piece on this exact topic over at Fangraphs (links to the article) just the other day. The gist of his article can be summed up in two sentences: "You can make it with a limited repertoire. It just has to be a good limited repertoire." Well, Rosenthal has a "good limited repertoire" right now, and one could argue that at the age of 23, he has the potential of developing one of his two breaking balls into a serviceable pitch to add to his weaponry.

Moving on from his repertoire, let's take a quick look at his pitch usage:

Rosenthal, as the set-up man and closer, loved his fastball, and with good reason. However, he was too predictable with his pitch usage to have sustained success as a starter at the big league level. First pitch? 87% chance it's a fastball. Behind in the count? 90% chance it's a fastball. Finally, as he moved ahead in the count or got to two strikes, he started using his secondary pitches. Hitters will pick up on this over time. Hopefully, with the amount of work he put into his stuff over the off-season, he has developed confidence to throw his changeup and breaking balls earlier in the count. As a starter, Rosenthal's pitch usage should look more like Wacha's from last season.

There is my case for giving Rosenthal a shot at the rotation this spring. He has the desire, repertoire, and stamina for the role. He may never become an elite starting pitcher, but does he really have to be? For how awesome he was last season, he accounted for 2.2 fWAR. The likelihood of him getting to that number on a consistent basis isn't all that great—as shown by his ZiPS projection of 1.6 for 2014. A starting pitcher's WAR can reach a level in one season that takes relievers multiple seasons to reach. He could have an average to above-average 2014 as a starter and still have a higher WAR than he did in 2013.

UPDATE: I contacted Dan Szymborski (the almighty ZiPS guy) to see if he could project Rosenthal as a starting pitcher in 2014. This is what he came up with: 13-7, 3.17 ERA, 118 ERA+, 2.9 WAR in 150.1 IP. These numbers are nothing spectacular, but for his first major league season as a starting pitcher, they would look very promising.

Finally, if he is unsuccessful as a starting pitcher, put him back in the bullpen. At his age, I really don't foresee a problem of him making the transition back into the closer role. If anything, it will make him more comfortable in his role knowing that the organization gave him the shot he had been hinting at for so long.

To me, it's simple: 15-20 years from now, I don't want to look back on his career asking "what if?" He's shown us what he can do in the bullpen; let's see what he can do in the rotation.

Until next time...

Joe

As usual, thank you to BrooksBaseball for the pitching data used in this post.

Rosenthal's minor league statistics were retrieved from minorleaguecentral.com.