Starting Pitcher Inning Shares

By Andy Singer

September 25th, 2023

Photo Credit: Christopher Pasatieri/Getty Images

***Note: All Statistics are as of Friday, September 22nd, 2023***

Now that the Yankees playoff hopes are officially over (they've been over for awhile, but now at least we don't have to hear the team and the New York media talk about a "special comeback"), I think it's time to start dissecting where the team stands today; what went wrong in 2023 (and longer); and how do you fix those issues? This is my first such post this year, and I'll probably have plenty more before the end of the year.

Through the season's first half, one of the team's few real strengths was its pitching staff. Yes, the bullpen was elite, but the starting rotation was sneaky good as well. Those numbers fell off completely in the second half as the Yankees' starters fought through a bevy of injuries and underperformance, and the rotation finished with just a 4.41 ERA/4.45 FIP/9.3 fWAR. Those aren't horrendous numbers, but they tell the story of a rotation that began the season with so much promise, but ultimately wilted.

That story was particularly true of the Yankees' bullpen, one of the top 2 or 3 bullpens in the league during the first half, but they too fell to Earth in the season's second half.

Over the last few seasons, one of the most oft heard reasons for the Yankees' bullpen fatigue and injuries is their overuse, particularly relative to the number of innings the Yankees' starters throw (or don't throw). I wanted to put that theory to the test for the 2023 season.

In the below screenshot, we'll see innings as a percentage of total innings from Yankee starters in 2023 and the top-10 teams in baseball as of September 22, 2023:

I'll be honest, I expected the Yankees to have the lowest percentage of innings pitched by a starting pitcher this season. Take your guesses before scrolling down to have the answers revealed:

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Here's the answer:

Most of the playoff caliber teams listed above have their starting pitchers toss at least 60% of their team's innings. There are exceptions to this rule, however. The Atlanta Braves just missed the cut-off, so they're probably in decent shape, though they have some injury concerns in their starting staff; the Rays manage their rotation and bullpen like no one else in baseball, utilizing an ace one or two other bulk starters, before playing matchups with the bullpen arms and bulk inning guys; and the Dodgers, who might be the only team to suffer more injuries than the Yankees in the rotation between 2022 and 2023, but they proved adept at adapting strategy to keep churning out wins.

Let's take a more granular look at inning shares. I wanted to know how many pitchers on each of these teams had crossed the 130 inning threshold in 2023:

Based on the above, it's pretty clear that teams should want at least 3 starters that can be 130+ inning "workhorses" (and yes, I'm aware that many of you will shudder at the use of workhorse and 130 innings in the same sentence) if you want to be in the playoff hunt. Texas must have made a deal with the devil, because they've managed to get innings from their entire opening rotation and the guys they acquired at the trade deadline who have thrown significant innings. Multiple teams with 3 starters who reached the 130 inning threshold have guys who just missed that threshold. The only team that doesn't have a starting pitcher who reached the 130 inning threshold is the Dodgers, and we've already gone over their predicament.

The long and the short of it is that yes, the Yankee starting rotation did put additional strain on the bullpen than most playoff bound teams do. One can either view the glass as half full or half empty. You could look at the above numbers and assume that with better health and one starting pitcher acquisition, the Yankees could very easily vault their innings share numbers into the realm of other playoff teams. The flipside to that is, we know what question marks face the Yankees this offseason. Behind Gerrit Cole, the Yankees have questions about the health of both Carlos Rodon and Nestor Cortes Jr.; Luis Severino has traditionally been counted on, and he has always either been hurt or in this year's case, underperformed, so he won't be back in all likelihood; Clarke Schmidt had an up-and-down season, though he did cross the 130 inning threshold...I just don't think his best role is as a starter; and Mike King has been a revelation, in that has proven that he can hold his devastating stuff through 6-7 innings, but he threw just 100ish innings this year, and there are concerns about how he'll hold up; and we have no idea if the Yankees have any real chance to add an impact arm on the trade market or in free agency.

There are a lot of ifs, ands, and buts there. The Yankees seem so very close when you look at the numbers just as numbers, but the context in which those numbers exist give me pause and some degree of pessimism. Stop me if you've heard this before: the success of the Yankee rotation next season depends strongly on health.