by Matt Wilkes

Rediscovering the fastball will be key for Sean Doolittle

When you have one dominant pitch, why not throw it a lot?

Pitchers across the game are adopting this mindset. Relievers, in particular, can get away with throwing one or two pitches heavily because they don’t see hitters more than once in a game.

New Reds reliever Sean Doolittle embraced this approach years ago. A whopping 87% of the pitches he’s thrown in his career have been fastballs. Only two pitchers have thrown a higher rate of fastballs since pitch tracking systems were installed in all 30 ballparks in 20081.

Since the heater was the driving force behind the stretches of dominance from Doolittle in the past, it only makes sense that it was the driving force in his performance decline the last two seasons. A quick look at the metrics confirms that suspicion.

Doolittle is giving up harder contact with his fastball and missing fewer bats — not a good combination. It’s unsurprising that he has 4.26 ERA, 4.70 FIP, and 5.29 xFIP the last two years.

What on earth happened to his four-seamer since 2018, his best season as a major-leaguer? The first place to start is velocity.

Doolittle’s fastball slowly lost some zip from 2016 to 2019 before completely falling off a cliff in 2020.

Injuries have undoubtedly played a role. Doolittle dealt with left arm fatigue and tendinitis in his right (plant) knee in 2019. The knee bothered him again in 2020, as he had a stint on the injured list due to “fatigue” in the joint. He later pulled an oblique on Sept. 10, which sidelined him for the rest of the season.

The knee is probably more important here since it’s a recurring issue. Notably, he had knee surgeries in 2009 and 2010 — which prompted the A’s to permanently move him from first base and outfield to pitcher — but it’s unclear if the recent problems are related.

Regardless, the legs are extremely crucial for a pitcher. They provide a stable base of strength that, in turn, fuel velocity. The front leg is more important for velocity. Reds director of pitching Kyle Boddy wrote about this a few years ago for Driveline. When a pitcher doesn’t have strength in the plant leg, they can’t transfer as much power from the back leg, resulting in diminished velocity.

Of course, a leg ailment can also throw off a pitcher’s mechanics. Here’s how Doolittle said the knee injury affected him in 2019 (per the Washington Post):

“When you get knee pain, the muscles on top of your knee shut down,” Doolittle said. “The glute shuts down. Your body is trying to protect it by saying: ‘Don’t use it. We’re not going to let you use it.’ It can lead to bad habits, and that’s a slippery slope.”

It clearly bothered him in 2020, too, well before he hit the IL. Through his first five appearances on the season, he was barely reaching 90 mph. When he returned in late August, he was hitting 91 — still not close to his previous velocity. His fastest heater on the season was just 92.3 mph. In previous years, he was topping out between 96 and 98.

Moreover, Doolittle was again struggling to get his mechanics in sync (per Todd Dybas of NBC Sports):

“Came out of the quarantine, physically, I was feeling good. Just my mechanics, my delivery was really, really out of sync. The last couple weeks of summer camp and first couple weeks of the season, I was trying a lot of things to get it to sync up.”

When he has his best velo, Doolittle lives at the top of the zone. He was among the early adopters of this league-wide trend. The southpaw did it without high spin rates, too — he’s typically fallen in the mediocre to below average range (around 2,200 rpm). Yet, between 2014 and 2018, he maintained a 29.7% whiff rate on his fastball, 9th-best among all relievers2. In 2018, only Josh Hader had a higher whiff rate on four-seamers than Doolittle.

At his best, Doolittle also got low-quality contact when hitters did connect. Only Tyler Clippard has a higher infield fly-ball rate than Doolittle (16.5%) since 20143. Pop-ups result in hits only 2% of the time, per Statcast data that dates back to 2015. If you’re going to give up contact, that’s the way to go.

Doolittle threw hard, but he certainly wasn’t in elite, Aroldis Chapman territory. Why was his fastball so effective? Why could Doolittle blow a 96-mph fastball by a hitter while someone like Wandy Peralta can’t do it with 99 mph gas?

Spin efficiency. Without a high raw spin rate, Doolittle relied on getting nearly perfect backspin on his fastball, counteracting the effects of gravity and keeping the ball up longer. This is what gave his fastball that extra “life” or made it appear to rise. Here’s a clip from 2018, Doolittle’s best season, to illustrate this4:

Poor José Peraza didn’t have a chance. Three straight fastballs — see ya later.

Doolittle starts over the middle of the plate, and Peraza fouls it away.

He’s on that one — let’s go a little higher, Doolittle probably thinks. Peraza tips it into the catcher’s mitt.

Alright, even higher this time. Based on Peraza’s free-swinging tendencies, Doolittle probably figured he’d get another swing. He did, and this one came up empty.

But really, few batters in any count are making contact with those last two pitches. Hitters have come to expect a certain amount of drop on fastballs — after all, they’ve seen thousands of them in their careers. A fastball with high spin efficiency doesn’t drop as expected, giving the illusion of “rise” and often resulting in swings underneath the ball that are either whiffs or weak pop-ups.

Here’s a perfect illustration of spin efficiency for a fastball:

The fastball with 100% spin efficiency is the one that stays up; the one with 40% ends up dropping the most.

Unfortunately, Statcast didn’t provide spin efficiency data until the 2019 season. But it does provide pitch movement data that dates back further. By looking at his vertical movement and where he ranks versus his peers, we can learn more about the “rise” on Doolittle’s fastball over the years driven by spin efficiency.

Other pitchers who are routinely atop these leaderboards include Clayton Kershaw, Justin Verlander, Josh Hader, and Walker Buehler.

Even with diminished movement in 2020, he was still solidly above average. A look at Statcast’s active spin leaderboard shows a small drop in spin efficiency from 2019. Doolittle spin efficiency fell from 92.1% in 2019 (60th in baseball) to 90.3% in 2020 (198th). It wasn’t significant, but it may have been enough to make his slower fastball even more hittable.

All eyes will be on the radar gun when Doolittle arrives to spring training in a couple of weeks. It’ll be the quickest way to get a gauge on his health. Will he be able to hit 95 mph again after an offseason of rehabbing? If so, the Reds may have a bullpen bargain on their hands. Even if he can’t get all the way back to his 2019 velocity, better results may come if he’s fixed his mechanics. Nothing is guaranteed, though, at this stage in his career.

Doolittle has spent time on the injured list in every season since 2014. He pitched only 12 games in 2015 due to a left shoulder strain. The following two seasons also saw him miss time due to shoulder issues. Then came the knee troubles. Doolittle’s age isn’t something to gloss over, either. He’s 34 years old, an age where many pitchers lose velocity and effectiveness even with a squeaky clean injury history.

If he no longer has that extra life on his fastball, pitching coach Derek Johnson may have Doolittle consider tossing his slider into the mix more often. Doolittle has typically kept it to a 4–5% usage rate, but he more than doubled that (12.6%) in limited action last season. Since 2017, when he reintroduced the pitch to his arsenal, the slider has held hitters to a strong 40.4% whiff rate and .153 xwOBA. It’s hard to tell how well the slider would perform across a larger sample, but it’s another option for Doolittle if his fastball doesn’t regain its former glory.

Maybe age and injuries have worn Doolittle down. Maybe not. The Reds clearly see enough to sign him to a low-risk deal. For the high-reward part of the deal to pay off, though, Doolittle will need some semblance of his old fastball.

Featured Image: All-Pro Reels

  1. Minimum of 250 innings
  2. Min. 250 swings against
  3. Min. 250 innings
  4. Videos courtesy of Baseball Savant

Matt got hooked on Reds baseball after attending his first game in Cinergy Field at 6 years old, and he hasn’t looked back. As a kid, he was often found imitating his favorite players — Ken Griffey Jr., Adam Dunn, Sean Casey, and Austin Kearns — in the backyard. When he finally went inside, he was leading the Reds to 162-0 seasons in MVP Baseball 2005 or keeping stats for whatever game was on TV. He started writing about baseball in 2014 and has become fascinated by analytics and all the new data in the game. Matt is also a graduate of The Ohio State University and currently lives in Columbus. Follow him on Twitter at @_MattWilkes.