Walker Buehler May Be Risking Arm Fatigue, but Neither the Dodgers Nor Buehler Are Worried

Are teams figuring out how to limit arm injuries to their best young pitchers? The Dodgers' management of Walker Buehler will help us understand.

GLENDALE, Ariz. — Major league teams are doing a better job protecting young pitchers’ health. We know this because young pitchers (like all pitchers) are throwing fewer innings, because advanced data is better at detecting fatigue, because Tommy John surgeries for major league pitchers are declining, and because my annual report on overworked pitchers hit an all-time low this year in the two decades I’ve been tracking them: one.

And that one pitcher is such an anomaly he threw his fastest pitch of the year in his last start of a season in which he took an 80-inning jump. Walker Buehler of the Dodgers hit 100.1 mph in Game 3 of the World Series.

“I don’t anticipate having any problems,” Buehler said. “The only thing the Dodgers said [this spring] is ease into your throwing a little bit.” And then the guy who loves to throw full tilt all the time laughed and said, “But that’s tough for me.”

I started out many years ago red-flagging all 25-and-under big league pitchers who increased their workload by 30 innings from their previous pro high (minor league innings included). Those pitchers were at risk of what I called The Year After Effect. The burden of adding too many innings at a young age often showed up the next year with regression, fatigue or injury.

Five years ago, following the kind of guidelines many clubs adopted, I amended the threshold to a 30% innings increase. Since then, here are the year-by-year numbers of young pitchers who absorbed a 30% innings jump, starting with 2014: 5, 5, 12, 3, 1.

Buehler, 24, who logged 178 innings over the majors and minors, was the lone young pitcher who jumped more than 30% last year. Kyle Freeland of the Rockies came close (+29%, based on +47 innings from his previous pro high in 2016).

Bottom line: teams are more careful than ever with young pitchers.

Asked about Buehler’s workload last year, Dodgers president Andrew Friedman said, “We talked about this at the beginning of spring training and the early part of the year. We don’t set out a set innings limit for guys. We have a range, but so much of it is how they bounce back outing to outing, how they maintain their stuff start to start, [and] how they’re bouncing back between starts that gives us more insight into fatigue, and that’s far and away the biggest indicator.”

When it comes to explaining this good news for young pitchers, let’s start with this: the growth in the supply and use of relief pitchers has taken the load off young pitchers. From 2008 to 2018 the number of 25-and-under qualified pitchers (one inning for every team game, or 162 innings in a full season) declined from 28 to 11, a 61% drop in a decade.

Moreover, the two seasons in the expansion era with the fewest 25-and-under qualified pitchers both occurred in the past two years. You’ll notice each of the past four seasons represented on this list:

Fewest 25U Qualified Pitchers in Expansion Era (1961–2018)

Year	U25 Qualified Pitchers
2017	11
2018	13
1995	14
2015	16
2016	17
2006	17
2005	17
1996	17

Now fold in the newly available data teams can use to identify what Friedman called “far and away” the biggest threat to pitchers’ arm health: fatigue. In the old days to monitor fatigue a pitching coach might say, “He’s getting the ball up. He looks tired.” Now to monitor fatigue teams can measure not only spin rate (see below re: Luis Severino), release point and spin axis and, but also muscle strength and recovery.

“We’re better [at detecting fatigue] than we were five years ago but not as good as we will be five years from now,” Friedman said.

The Dodgers, for instance, would give Buehler an extra day or so of rest on the basis of routine monitoring. They gave him five days or more of rest in 21 of his 28 major league appearances, postseason included. He never made back-to-back appearances on four days of rest.

“We gave him little blows to get his legs underneath him from time to time,” Friedman said.

Buehler more than maintained his stuff over the course of seven months. In fact, as the metrics of his fastball show, he got stronger:

Buehler 2018 Four-Seam Fastball Metrics

	MPH	RPM	BAA
Regular Season	96.2	2,415	.176
Postseason	97.5	2,425	.156

By giving young pitchers fewer innings and more monitoring, major league teams quietly have stabilized what used to be an epidemic of Tommy John surgeries. Based on reported surgeries, from 2012-15 an average of 27 major league pitchers per year underwent Tommy John surgery. From 2016-18 that average has dropped to 19.

(Another factor in the drop may be that more pitchers are getting the surgery before they become big leaguers. Buehler, for instance, underwent Tommy John surgery upon being drafted by the Dodgers in 2015.)

When it comes to his workload, Buehler likes to point out that in 2014, between his work at Vanderbilt and the Cape Cod League, he logged about 140 innings. (He also blew out his elbow the year after). His goal this year, and all subsequent ones, is to throw at least 200 innings.

“To me, that’s what big-time starters do,” he said.

Such an achievement would be shocking in today’s new world of protecting pitchers. Buehler is entering his age-24 season. Until 2016, there had never been a full season in major league history in which no pitcher under 24 reached 200 regular season innings.

Then nobody that young reached 200 innings in 2016 … and nobody again in 2017 … and nobody again in 2018.

The 2018 Year After Effect Report Card

Last year I flagged three young pitchers as at risk for regression based on their 2017 jump in innings. All three regressed:

Luis Severino, Yankees

This might be the best comp to what the Dodgers must look for with Buehler in 2019. Severino (+58 innings,  +38.3% in 2017) remained healthy, but regressed slightly across the board, a decline due entirely to a 10-start stretch from July 7 to September 5 when the 2017 innings bump caught up with him. During the tail end of that struggle, Yankees pitching coach Larry Rothschild told the New York Post, “If you look back at the history of younger pitchers who pitched as much last year with that kind of increase in innings, including the playoffs, you will often find an eight- to 10-game stretch like we are seeing now. This is not out of the norm.”

The Yankees did give Severino a 10-day rest around the All-Star break, but otherwise kept pitching him on the fifth day in seven of those 10 starts. You could tell Severino grew fatigued by the decline in his slider, which lost almost 150 rpms and much of its bite. Here is the evidence of how he lost his slider when he hit the wall in July and August, and how he got it back:

Severino 2018 Monthly Slider Spin Rate

Month	RPM	BAA
April	2,917	.143
May	2,885	.150
June	2,923	.164
July	2,878	.263
August	2,772	.255
September	2,846	.227
October	2,859	.200

Luiz Gohara, Braves

The former top lefthanded prospect threw only 77 2/3 professional innings in a nightmarish season marred by the death of his father, various injuries and carrying too much weight. He fastball dropped from 97 mph to 94.6 mph.

Dylan Bundy, Orioles

He led the league in losses (16) and home runs allowed (41) while his ERA ballooned from 4.24 to 5.45. Arm strength was an issue. Check out how the metrics declined on his fastball:

Bundy Four-Seam Fastball Metrics

Year	MPH	RPM	AVG
2017	92.2	2,485	.288
2018	91.6	2,416	.302