Sean Doolittle has been a reliable and often devastating reliever for the Oakland Athletics since making his rookie debut in 2012. While Sean’s name might not be one of the first that comes to mind when asked to name a dominant reliever the past half-decade, it should be as he has the resume to back it up. I’m not just talking about the three postseasons and one All-Star Game he appeared in.
Since his debut in 2012, 141 relievers have thrown at least 200 total innings according to Baseball Reference’s Play Index. Among those 141 relievers, Doolittle ranks eighth in OPS+, eighth in FIP, 14th in strikeout rate, and sixth in walk rate. He’s also had the third-lowest inherited runner scoring rate. In fact, since his debut, no reliever has thrown a higher percentage of strikes than Doolittle’s 71 percent, which is tied with Koji Uehara for tops in all of baseball.
Sean does have an Achilles heel that has really held his performance back the last three seasons: injuries. Doolittle was plagued with injuries that started at the beginning of the 2015 calendar year and have continued to impede him ever since. They’re no doubt responsible for virtually all of the struggles he’s had the last three seasons.
Since making his major league debut in 2012 through the 2014 season, Doolittle saw the disabled list just twice. In September 2012 he missed two games with a shin contusion after taking a batted ball off the leg. They only other time he missed any time was at the end of August 2014 for 19 days with a right ribcage strain.
Perhaps the rib cage strain would foreshadow a changing of the tides as injuries really started to affect him from day one of 2015. In January the Oakland Athletics announced Sean was dealing with a slight tear in his right rotator cuff as well as inflammation and irritation in his throwing shoulder. It took him 50 days from Oakland’s opening game to make his season debut, and it would be short-lived. He tossed a scoreless inning against the Tigers and was almost immediately re-added to the disabled list for another shoulder injury in his throwing arm. He would remain there for 87 days, not returning until August 23rd, 2015.
The 2016 season started out better than expected, but then on June 25th, 2016 Doolittle strained his left shoulder, which caused him to be placed on the disabled list again. He made his return on September 5th against the Angels, pitching a scoreless inning and recording two strikeouts. It was Sean’s first major league appearance in 71 days.
Doolittle was also bitten with the injury bug this season, as he strained his left shoulder between outings in April and was sidelined yet again. He was activated again on June 10th making his first appearance in 41 days with a scoreless eighth inning in a 7-2 win over Tampa Bay.
Over the past three seasons, the injuries have really took their toll on Sean Doolittle. Not only are they negatively affecting him statistically, his fastball velocity has also suffered greatly.
2015 was by all accounts his worst season ever, in terms of results, velocity, and health. He appeared in only 15 games, barely recording over a dozen innings, and his results were atrocious — he gave up six runs on 12 hits and five walks. All career worsts in terms of average over time. His fastball velocity was a career low 93.2 miles per hour according to Statcast. His career average is 94.7 miles per hour.
Doolittle’s 2016 season started out with three outstanding months of solid outings where his batting average against was .218 with a walk rate of 6.6 percent and a strikeout rate of 29 percent. Then he had his injury, and upon returning he struggled, allowing a .275 batting average and four earned runs in just over eight innings.
Doolittle’s injuries and struggles toward the end of 2016 led to questions about his health and performance as we moved into the 2017 season. FanGraphs’ Eno Sarris even touched on this topic back early in April. Despite questions about his performance and health, Doolittle finished with a solid month of April; in just shy of eight innings, he allowed five hits and one walk versus 11 strikeouts.
Unfortunately, healthiness for Sean was short-lived, as I mentioned earlier. However, since returning on June 10th, he has been almost literally unhittable. In six innings of work he has allowed a single hit, no walks, and 11 strikeouts. He also inherited two runners, neither of which have scored.
Regardless of his health, the key to Sean Doolittle’s success are his swing-and-miss pitches. His four-seam fastball and slider are the primary pitches, and the ones he receives the whiffs from.
When comparing his 2015, 2016 and current numbers, we can see that his slider is receiving whiffs like never before and he’s also using that pitch more as well. In addition, his four-seam fastball whiff rate is directly in line with what it was last season, when he had an overall successful year, and is also higher than the 2015 season in which he struggled with performance and health issues.
Furthermore, the whiffs are coming outside the strike zone, as the chart below shows. When he receives a greater number of swinging strikes, they are swinging strikes on pitches out of the strike zone rather than pitches in the zone.
Further evidence of this is Doolittle’s high out-of-zone swing rate, which is currently 46 percent, ranking second only to Roberto Osuna. Meanwhile, his out of zone contact percentage is almost right in the middle, placed 274th out of 475 pitchers this season.
Apart from the injury early in the season, Sean Doolittle is off to a career year. He’s pitched 14 2⁄3 innings while allowing just six hits and one walk. This means his walk rate is about two percent, which is good for fourth in the majors among all pitchers with at least 10 innings. He’s struck out 22 so his strikeout rate is just over 42 percent, good for sixth in the league. He’s also sixth in swinging strike percentage with just over 18 percent, thanks to the high number of swings-and-misses out of the zone.
So if Doolittle is able to remain healthy as the season approaches the halfway point and beyond, he could finish with career-best numbers. That would re-cement him as one of the best relievers in the game and a hot commodity, especially as a left-hander, should Oakland look to try to deal him.
Ron Wolschleger is a Contributing Writer for Beyond the Box Score as well as Bless You Boys. You can follow him on Twitter at @FIPmyWHIP.