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What would happen if Aroldis Chapman were to start? Or Max Scherzer were to close? It’s a strange invisible fence that seems to separate the roles of starter and reliever. If the Nationals wanted to, they could use Scherzer in relief. The Reds would have to stretch Chapman out a bit, but they could choose to make him a starter. And the world would continue spinning. It’s a maddening question, but despite the constant pleas of the listenership of Effectively Wild, no team seems willing to run the experiment that would answer it. Pitchers either pitch seven innings or they pitch one. (Unless they pitch for Tampa Bay.)

We kind of have an idea of what would probably happen. In fact, we have a tiny bit of data. Henry Druschel recently looked at how starters fared when sent to the pen in the playoffs. The results were a little confusing (the sample size was also small), in that starters-turned-relievers gave up more walks, struck fewer batters out … and gave up fewer runs than they did in the regular season. Weird.

The general consensus is usually that as a starter, a pitcher has to pace himself a bit, because he’ll (hopefully) be out there for six or seven innings and he’ll have to turn the lineup over twice. As a reliever, he’ll be out there for one inning and he can just let it fly. Relievers, in general, have higher strikeout rates than their starting counterparts. It makes sense. If you don’t have to pace yourself, reaching back for that extra gear is something you can do for every hitter you face. All four of them. Turn a starter into a reliever and he’ll turn into a monster.

Teams also seem to have made up their minds on which job is harder. The top starters in baseball make upwards of $25 million. The top closers might get $15 million. And there’s something to be said for the fact that there are plenty of guys around who are former (failed) starters who have found a second life as a bullpen arm, while there aren’t that many former relievers in rotations today. Seems as though while relievers have better numbers, starting is actually a harder gig. So, we should expect an ace starter to be the best closer ever if he were put into that role, and perhaps an ace closer to be a good starter.

But from a research perspective, we’re missing something. We know how relievers and starters seem to perform differently, but it’s still two entirely different groups of guys in each basket. What if Aroldis Chapman, by having to pace himself, would completely lose what makes him amazing? What if Max Scherzer the closer would still be a good pitcher, but the pacing thing didn’t really make much of a difference? We need to find some way to look at what happens to the same guy (or set of guys) when they are starting and when they are relieving.

Warning! Gory Mathematical Details Ahead!
We won’t be able to get a good sample of players who start and relieve in the same season. There are a few, of course, but we also have to realize that a good way to “become” a reliever is to get hurt (are we seeing the effects of a transition to relief, or are you just hurt?), to get demoted (are we seeing improvement because you hit some bad luck as a starter and are now regressing to the mean?) or to simply have the calendar year change over and the team’s needs change (are you the same person you were last year?).

Instead, I’d suggest we look at it a different way. Relief appearances come in different shapes and sizes. While the standard relief appearance these days is one inning or less, there are times when a reliever is asked to go a little deeper. Sometimes, he’s the long man that night. Sometimes, the manager just wants him to get three innings to finish off a game. In those outings, our reliever is not needing to pitch six innings, but he will have to pace himself and potentially think about turning the lineup over a bit.

Using data from 2003-14, I looked for all relief appearances in which the pitcher faced more than 12 batters. It’s possible that in a few of those, he didn’t go out there expecting to face 12 batters, but for the most part, he knew what he was getting into. I also looked for all appearances in which a reliever faced six batters or fewer. It’s likely then that he knew he’d only be out there for an inning or so and he could just let it go. In this way, we can at least see what pacing does to a pitcher’s performance. It’s not a perfect match for starting, but it does have some of what we’re looking for. I looked for pitchers who had at least five appearances of both kinds within a year.

Using the log-odds method, I calculated the chances that, based on the pitcher’s seasonal stats and those of the batter he was facing, a plate appearance would end in a strikeout. (I later did the same for walks, singles, etc.) I used this as a control variable within a binary logistic regression, and then coded for whether the plate appearance took place during an outing of fewer than six batters or one of 12 or greater. (Plate appearances with six to 11 batters faced were not included.) If a pitcher was more likely to strike a batter out in a short appearance vs. a long one, we’d see it in the long vs. short variable.

The results? When a pitcher in this sample was pitching in a short appearance, his strikeout rate was much higher, on the order of about 1.5 percentage points for the average pitcher in the sample. That was the only finding that was statistically significant among the outcomes. Walks were marginally so (p = .147 … which, yeah, that’s stretching it) but that arrow also pointed toward more walks in a short outing for the same pitcher. Singles went down in short outings (p = .120, so again, take that for what it’s worth), and overall OBP was not affected, nor were extra base hits or home runs. And while overall BABIP wasn’t affected, the chances that the ball would be put into play were significantly impacted. When a pitcher was pitching a longer outing, significantly more of the batters he faced put the ball in play.

What’s fascinating is that when a reliever had to pace himself, he was clearly using a different, pitch-to-contact approach, but overall results weren’t affected much. The way in which he got outs changed somewhat from strikeouts to ground outs and pop flies, and the way he put runners on first changed from walks to singles, but the results were just different. Not better or worse.

Now, the question is usually asked about the elite pitchers. Scherzer and Chapman. The guys in this sample are bouncing around roles in the bullpen, probably picking up whatever work happens to be available. They’re probably not elite. They’re probably doing that job not because the manager thinks they are perfect for the gig, but because the team needed warm bodies to go out there and do it. The idea of pitching to contact makes sense given the demands of the assignment, so maybe it’s just reasonable professionals doing what needs to be done. Interpret with care.

These data suggest that someone like Aroldis Chapman would lose some of his strikeout mojo in the rotation (and, of course, the reason that people are obsessed with him to begin with is because of the strikeout mojo). Scherzer might pick up a little on his K rate, but he might also issue a few extra walks. He might be a more electric pitcher, but that’s not always the same thing as being a better one.

We’ll Never Know…
Of course, other than the occasional Game 7 stint on the mound for an ace pitcher, we’ll never have a big enough data set to really answer this question. Still, I think we have a bit of direction and a bit of warning on something to watch out for when we theorize on the matter. I think that line of reasoning when people think about this goes something like:

  1. Aroldis Chapman is good. (True.)

  2. Aroldis Chapman strikes out a lot of guys. (True.)

  3. Aroldis Chapman is good because he strikes out a lot of guys. (There is of course, some truth to this, but there’s more to pitching than just strikeouts.)

  4. If Aroldis Chapman started, he might lose some of those strikeouts. (Probably.)

  5. This means Aroldis Chapman wouldn’t be as good. (Maybe, maybe not. He might lose some K power, but what if he also stops walking more than four batters per nine?)

Chapman would still have an electric arm, and even if he had to sit lower in velocity to make it through six innings (perhaps throwing 96 on a regular basis), he’d still use velocity as a key part of his game plan. Maybe he’d use it in a slightly different way, aiming for weak contact, rather than just a swing and miss. But does Chapman have the skills to do that consistently. If he’s not throwing “You can’t touch this” stuff, but merely 96, can he hit his spots to actually get the swing and the not-quite-on-the-sweetspot contact? Maybe.

It’s good to remember that when we do these sorts of analyses and then project our conclusions out onto people who weren’t actually in the data set, we need to be careful. Pitching coaches and managers are essentially paid to introduce bias into our data sets. When we study fielding at third base, we’re looking at the 30 or so guys whom MLB managers thought were the best option at third base. If we assume that managers have some idea of what they are doing, we shouldn’t quickly assume that this second base guy over here would do the same if he were moved to third. In the same way, maybe the reason Chapman isn’t a starter right now is that the Reds honestly believe that he’d be a bad one, or at least a mediocre one, and that his value as a closer would eclipse his value as a starter. It’s always possible that they are wrong, but don’t be quick to assume that.

To answer the question at hand, the data here give us some idea of what to expect. If Chapman and Scherzer switched roles, they’d probably pitch a little differently than they do now on account of the role. And that would have an effect on them and the results would take a different form. But the best guess that we can make is that, overall, they’d be about as effective as they are in their current role.

Thank you for reading

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lichtman
8/04
We can assume that the pitcher will gain or lose a mph when converting and we know how much that is worth (1/3 run per mph?). We also know what the times through the order is worth (1/3 of a run per TTO). And we know that pitchers with fewer pitches in their repertoire get hurt a little more in the TTOP (and vice versa). So I think we can make a pretty good assumption about the increase or decrease in rpg when converting. We don't know about the stamina factor, especially for reliever to starter conversion. I think it is a safe bet that some relievers simply don't have the stamina for that. Of course we don't know which ones. Finally, I don't think you can use the sample you are using for this kind of analysis. To much selective sampling (actually I am surprised at the results given that). When a reliever pitches a few innings, he is likely to be pitching well and when he doesn't he is slightly likely to have pitched poorly.
pizzacutter
8/04
I'll grant that this isn't ideal methodology, but it's at least one analog that we have actual data on.
lichtman
8/04
I don't know how you dismiss it. I think it is a fatal error, not accounting for that selection bias. And I'm not really sure that you CAN account for it, especially when you are looking for some small differences. You can almost never use playing time either in-game or season-long, and expect it to be independent of performance, especially in-game (for pitchers of course).
LlarryA
8/04
You're right to mention stamina, because that's such an attractive trap. It easy to think we "know" about stamina, since we see pitchers stretched out at various times: late in the spring; while returning from injury; or even those prospective starters who get their first taste of the majors in the bullpen. But those are specific and different circumstances, so we need to watch what conclusions we try to draw from that. To me the bigger and more intriguing unknown that Russell mentions is the effect upon command and control. If the super closer (Chapman) slows down in order to pace himself, does he make sufficient gains in control (and is there a learning curve for him there)? We have some data going the other way: do starters get wilder (and how much) when they air it out for 1 inning? But how much of a sample base do wee have for that, and how applicable is it really?
morro089
8/04
And you also have the "better get to [the starter] early before he settles in" theory (that I think was researched and shown to be true in by BP). So as Chapman would go along his control would get better. Or Scherzer's command wouldn't be as strong in his one inning. I'm surprised Russell never went into this because I think that theory plays a lot into his command thoughts.
shmage
8/04
Just a couple of names. S then R: Dennis Eckersley. R then S: Clem Labine
morillos
8/04
And another S then R: John Smoltz.
bleaklewis
8/04
Another starter turned reliever: Mike Marshall. If we had the pitch f/x data from back in the day he would be an interesting guy to study. His Cy Young year he pitched in a 106 games and threw 200+ innings in relief.
LlarryA
8/04
Derek Lowe was the first R->S conversion guy I thought of, but there'll never be enough of that kind of guy to be more than anecdotal.
jwferg
8/04
Add in Adam Wainwright, Curt Schilling, and Dennis Martinez to those who started in the Pen and then transitioned into real pitchers.
hyprvypr
8/04
What about a baseball roll of the long-closer. A guy, like Sherzer that could pitch every other day and go two, maybe three innings and still have lights-out stuff? A quality team could use a guy like that and each day they had the lead after six would be a 95% win scenario.
stonepie
8/04
how about just a few guys throwing 3 innings a night, 2-3 times a week. owners would love this because you wouldnt have to pay top starters anymore but players would rebel.
huztlers
8/04
That is not a realistic role. Pitching one inning regularly is pushing it, but multiple innings regularly would destroy an arm - especially if they were putting any effort into it. We have all seen a closer go 1+ and be unavailable for a few days... what you are suggesting would be that on a regular basis... only a twice as long.
ADprospectus
8/04
"If Chapman and Scherzer switched roles, they'd probably pitch a little differently than they do now on account of the role. ...But the best guess that we can make is that, overall, they'd be about as effective as they are in their current role." If the Reds believed Chapman could be as effective in a starting role as he has been in a closing role, why wouldn't they be using him as a starter and have him pitch 160-180 effective innings per season, rather than just 60-80?
pizzacutter
8/04
I guess I'd amend that sentence to include "all else equal." A couple of paragraphs earlier, I talk about how it might not be the case in the specific. Chapman would probably have to lay off the 101 mph stuff and settle for "only" 96. Could he do that and still be effective? Maybe. I will grant that there are a lot of variables that we can't account for here. My goal was to look at what precious little data we could grab on this question.
JanFortyTwo
8/05
One important reason against Chapman as a starter: he doesn't want to start, at least he did not want to do it before the 2013 season: espn.go.com/mlb/spring2013/story/_/id/9062111/aroldis-chapman-cincinnati-reds-wants-close
Lagniappe
8/04
To the above examples, Dave Righetti, Bob Stanley are two more examples. Less prominent is Jesse Chavez. In tiers, Russell's argument appears to valid. In earlier days a lot of young pitchers started as relievers so their data are all available too.
Lagniappe
8/04
To the above examples, Dave Righetti, Bob Stanley are two more examples. Less prominent is Jesse Chavez. In tiers, Russell's argument appears to valid. In earlier days a lot of young pitchers started as relievers so their data are all available too.
onegameref
8/04
Going way back to the 70's, Wilbur Wood transitioned quite nicely from bullpen to starter. Being a knuckleballer helped for sure. Charlie Hough as well. Guys breaking in as relievers is certainly more common no? Sale and Buerhle for example. I wish some team would make a concerted effort to train their minor league relievers to pitch 2 or more innings to strengthen their arms, but also to expose them more to hitters from both sides of the plate and in how to manage their exertion on pitches. I think it would be helpful for pitchers slated for the late innings based on stuff to learn more about how to manage their strengths and weaknesses like I suspect major league starters must.
NightmareRec0n
8/05
I thought of this when there was trade talk about Chapman. Imagine if a team like the Dbacks actually tried him as a starter again, especially considering the progress with his Changeup? It isn't likely...just a thought given a team that still sees starter potentially could extract a stupid amount of value if it worked.
lichtman
8/05
There is not that much difference between the value of a closer and a starter. If a closer pitches 70 innings at an average leverage of 2.3, that is the equivalent of 160 starter IP.