Danny Duffy’s good numbers this year are supported by an increase in fastball velocity, along with much improved strikeout and walk rates.
After opening the year in the bullpen for the Kansas City Royals, Danny Duffy was moved to the starting rotation in mid-May. His numbers as both a starter and reliever show that he’s taken a big step forward this season. Duffy pitched in relief in his first 16 appearances and had a 3.00 ERA in 18 innings. He had a strong strikeout rate (10.5 K/9) and was doing a good job of limiting walks (2.5 BB/9) while pitching mostly in low leverage situations. When Chris Young and Kris Medlen were placed on the DL, it was Duffy and Dillon Gee who were called upon to join the starting rotation.
It took a few games for Duffy to get stretched out. He tossed 48 pitches in his first start of the season on May 15 when he pitched three scoreless innings with five strikeouts. He made 63 pitches in his next start, a 4 1/3 innings outing in which he held the White Sox Scoreless and struck out three. He faced the White Sox again in his next start and cruised threw five scoreless innings before running into trouble in the sixth when he was dinged for two long balls and five runs. He ended up throwing 76 pitches in 5 1/3 innings.
Duffy pitched six full innings for the first time of the year in his start against the Tampa Bay Rays on June 1. In six innings, he allowed three runs on seven hits while striking out six and walking none. He followed that up with a good start against the Baltimore Orioles that saw him pitch 6 1/3 innings with nine strikeouts. He gave up two earned runs, both on solo homers. Duffy had his best start of the season on June 11 against the White Sox when he pitched six scoreless innings, allowed three hits, three walks, and struck out 10. He threw 88 pitches in that game, so he should be close to stretched out at this point. Overall, he’s 2-1 with a 2.90 ERA and 0.97 WHIP in his six starts this season. Even more important, he’s struck out 38 batters in 31 innings with just five walks.
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The Royals drafted Duffy way back in 2007 with the second pick of the third round (96th pick overall). Baseball America had Duffy ranked in the Kansas City Royals’ Top 10 every year from 2007 to 2010 and he made the Baseball America Top 100 prior to the 2011 season when he was ranked 68th. A left-handed pitcher with a 95 mph hour fastball is a highly desirable commodity in baseball. The Royals were hoping he would be their young ace. His first taste of big league play did not go well. He made his Major League debut in 2011 but really struggled with control, as he walked 51 batters in 105 1/3 innings. He had a 5.64 ERA and 1.61 WHIP.
Duffy made just six starts in 2012 before his season ended with a DL stint that led to Tommy John surgery. The injury limited him to 11 starts total in 2012 and 2013. Notably, before the injury Duffy’s average fastball velocity was 95.3 mph. After the injury, his fastball averaged 93.7 mph.
The 2014 season saw Duffy come back from injury to set career highs in starts, innings, and wins. He had a 2.53 ERA and 1.11 WHIP in 149 1/3 innings. That looks like a great year, but a big part of that impressive ERA was a very low, likely unsustainable, .239 BABIP (Batting Average on Balls In Play). Duffy had a 3.83 FIP and 4.42 xFIP that year and his strikeout rate was 6.8 K/9, which was a full strikeout below his career rate coming into the season. The good news was that Duffy started 25 games. The bad news was his fastball was still two ticks below what it had been prior to his Tommy John surgery.
Back in the Royals’ rotation at the start of last season, Duffy really struggled through his first eight starts. He averaged fewer than five innings per start and had a 5.87 ERA and 1.70 WHIP, with 19 walks in 38 1/3 innings. After allowing 14 earned runs in 9 2/3 innings across three starts, Duffy was put on the DL on May 17 with left biceps tendinitis. He missed 38 days, but was much improved when he returned. He made 16 starts and four relief appearances and closed out the year with a 3.39 ERA and 1.27 WHIP in 98 1/3 innings, while striking out 72 and walking 34. Of note, his fastball velocity was back up in the 95 mph range in the four relief outings he had in September.
Through 49 innings this season, Duffy has a 2.94 ERA and 1.06 WHIP. His ERA estimators are very close to his ERA (3.09 FIP, 3.30 xFIP). His strikeout rate (10.8 K/9) is up from last year by more than four strikeouts per nine innings and he’s shown by far the best control of his career, with a 1.8 BB/9. That’s two fewer walks per nine innings than Duffy averaged in the first five years of his career. He also appears to be fully healthy again, with an average fastball velocity (per Pitch f/x) of 95.9 mph, even faster than before he had Tommy John surgery.
Also according to Pitch f/x, Duffy has changed his pitch repertoire. In the first five years of his career, he predominantly threw four-seam fastballs (roughly 65% of the time). This year, he’s throwing 50% four-seam fastballs and 21% two-seamers. He’s also throwing his two-seam fastball nearly as fast as his four-seam fastball. In fact, it’s been his most effective pitch this season.
Duffy’s strong improvements in his strikeout and walk rate can be seen through his plate discipline numbers. His first strike percentage is 66.8%, which is the first time in his career that he’s thrown strikes on the first pitch more than 60% of the time. His improved control has induced more swings on pitches both in and out of the zone, but batters are making contact at a much lower rate (69% this season) than they had over the previous two seasons (roughly 83% contact rate). He has a career-best 17.3% Swinging Strike rate and that rate has held up as a starter. For starting pitchers with a minimum of 30 innings so far this year, Duffy’s 16.7% swinging strike rate is the best in baseball. Clayton Kershaw, Jose Fernandez, Max Scherzer, and Noah Syndergaard are the next four in this category. That’s good company to keep.
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He’s only thrown 49 innings so far, but Danny Duffy has shown real improvement this year. His fastball velocity is back up to peak levels. He’s throwing more strikes than he ever has and is getting more swings and misses than ever before. The starting pitchers of the Kansas City Royals currently have the third-lowest WAR (per Baseball-Reference) in baseball and are 26th in ERA, but Danny Duffy has been a bright and shining light on a staff with many disappointments.