The Case for a Six Man Rotation

The Case for a Six Man Rotation

After what became of the 2020 season, baseball fans should continue to expect the unexpected in 2021. Luckily for the New York Yankees, they made astute and speculative pitching signings in the offseason. So what can the Bombers do to embrace the chaos and power forward with health, safety, and winning in mind? Incorporate a six man rotation.

Here, I’ll dig into the health risks and their manifestation in 2020, a statistical approach to the idea, and the feasibility for the Yankees starting the season with a six man rotation.

A Pitching Pandemic

When the 2020 season was shortened due to our ongoing pandemic, there were fears we would see a drastic increase in injuries for pitchers. Teams needed to ramp up quickly, praying pitchers maintained arm strength and flexibility during quarantine away from coaches and dependable facilities.

But as a list of MLB-level pitchers on the Tommy John Surgery List Google Sheet by @MLBPlayerAnalys shows, the overall fear was realized. We saw 7 more TJ surgeries in ‘20 than in all of ‘19. This season, pitchers should expect an even greater challenge of maintaining their health this season while rediscovering the groove of a full 162-game stretch.

Let’s say what we all know, throwing a baseball really hard is really bad for you. There’s nothing normal about a person’s arm traveling “from up to 175 degrees of external rotation to 100 degrees of internal rotation in just .042 of a second.” Take your top-of-the-rotation starter, add 200+ innings of around 15 pitches per inning and tell me you don’t want to immediately ice your arm. That doesn’t even factor in the further torque and stress that come from hucking breaking balls.

The science is incontrovertible. But since pitchers are professional athletes gain big incentives to assume that risk, the choice by management and baseball operations teams to reduce workload, add rest and increase recovery time for their starting staffs can abate the inherent strain. That’s the benefit of adding another a sixth man to the rotation.

A Statistical Approach

Crediting Fangraphs writer Ben Clemens for his deep dive using xFIP and ERA, we have an idea of the numbers favoring the statistical approach. 

Assuming a five man rotation with six innings per start and a full 162-game slate, starters across the MLB would be hurling 192 innings. Adding a sixth starter introduces an extra day of rest for each and slashes their workloads by 30 innings.

While that‘s a wide approximation, Ben goes further. He focuses on xFIP to see the statistical significance to the change. In his own words, the extra day of rest doesn’t appear to be worth that much.” Using 2020 starter numbers and 1,291 qualified starts under his approximations, each extra day of rest correlated to an improved xFIP by ~0.06 relative to their seasonal average and a potential 6.5 runs saved over the course of the season.

Ben then focuses on ERA to view the costs of adding a starter to each team’s rotation. Plugging in the sixth man on the depth chart and using the innings approximation from earlier, the data shows teams like the Royals and Orioles would benefit most, only forfeiting about ~3 runs each over the course of the season. The Yankees find themselves at the bottom of the list, giving up around 12 runs more or a little over 1 win on season.

It’s small. But coupled with the implied injury benefit from earlier, it’s wise with the costs so low. Two teams pledged to adopt a six man rotation: the Mariners and Tigers. The Red Sox alluded to the same before spring training. After coming off an erratic season with young arms that need a cautious approach, it’s a no-brainer for all three franchises. Is it the same for the Yankees?

A Six Man Rotation Can Work for the Yankees

Penciling in Gerrit Cole, Corey Kluber, Jameson Taillon, and Jordan Montgomery as the top 4 starters, here are the leftover starters: 

A proven MLB arm in Domingo Germán, the two top pitchers in the system in Deivi Garcia and Clarke Schmidt, and a highly valued sophomore in Michael King. We don’t know when Luis Severino may be able to return from Tommy John, but a late summer debut isn’t out of the question.

Germán is odds on for the 5th spot given his strong spring, but it’s clear the young guns are ready for more innings at the top level. Each of those men have at least one minor league option for 2021, but the indefinite loss of Zack Britton provides an opening.

Rather than replacing Britton with one of the non-roster invitee left-handed relievers, the Yankees can and should retain one of those young arms as the sixth man of a six man rotation. Lightening the load on Kluber and Taillon, both of whom are coming back from major injuries, can only help their health and longevity throughout the season and allow valuable innings to go to pitchers hungry to make an impression. Given he was confident enough in his stuff to afford him a postseason start last season, Aaron Boone’s clear choice for a sixth starter would be Deivi Garcia.

We’ll just have to see what shakes out over the next few weeks of spring training.

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