Danny Duffy made his Major League debut on May 18 with a tough assignment against the Texas Rangers. Not too surprisingly, he only lasted four innings after walking six batters. The 22-year old lefty was promoted after throwing 42.0 innings at Triple-A and posting strong skills including a 48/10 K:BB ratio. So far with a 4.58 ERA and 104 xFIP-, he has not embarrassed himself, but has probably been a bit of a disappointment for fans of his.
As what usually happens when a starter transitions to the Majors, Duffy’s strikeout rate has dropped. After never falling below the 8.9 mark at any stop during his minor league journey, his K/9 sits at a decent, and still above league average, 7.5. His SwStk% and Contact% are exactly at the league average marks, so his K/9 at this moment looks to be around where it should be, if not a smidge too high.
Control has been the biggest issue. While he has struggled with this at times in the minors, it has always come during very small samples and was much better over longer periods of time. His F-Strike% is just 51.7%, well below the 59.1% league average, and supports the poor walk rate. Given the good control he has displayed during most of his time down on the farm, I would expect his walk rate to steadily improve. Unfortunately, Duffy has a neutral batted ball profile, and was similarly ground ball neutral in the minors. That is not too terrible though as Kauffman Stadium depresses home runs rather significantly.
The good news is that his pitch repertoire looks rather impressive. He features a fastball that has averaged 93.5 miles per hour, which would be above average for a righty, but being a lefty, this is an excellent mark. In fact, this ranks him third amongst all lefty starters in baseball in velocity. He also throws a curve and change-up over 10% of the time, and has thrown in a slider every once in a while.
Now back to the question I posed in the post title. In July, Duffy has struck out a batter per inning and only walked four in three starts over 18 innings. Now, I am not typically one to even mention such a small sample of starts, but for a rookie pitcher, it could carry some significance as he continues to gain experience and make adjustments. His July xFIP is just 2.96, whereas his May and June marks were well above 4.00. The Royals actually have a pretty good defense for a change, ranking seventh in baseball in UZR/150. Even their offense has been decent, as they find themselves in the middle of the pack in wOBA. With quality stuff, a surprisingly decent team supporting him on both offense and defense, and a forgiving home park, Duffy looks like an interesting guy to go after in deeper leagues and a good target in keepers.