His performance when on the field was solid, but Duffy's 2017 season was marred by injuries and a DUI arrest. The lefty missed more than a month in the middle of the campaign with an oblique issue and later battled elbow inflammation. Surgery was ultimately deemed necessary to remove loose bodies from the elbow, but Duffy was expected to have a normal offseason. Duffy's strikeout rate fell from 25.7 percent to 21.4 percent last year, coinciding with a two-mph drop in average fastball velocity, but nevertheless he shaved nearly 40 points off his FIP thanks to sharp control and a reduction in home-run rate. He continues to post dramatic platoon splits, with righties beating up on him (.329 wOBA last season) while lefties flounder (.199 wOBA), and at this point it seems he may never figure out right-handers, but there is some hope that Duffy's velocity and K-rate will rebound with better health in 2018.

Duffy had a breakout season in transitioning to the rotation from the bullpen after two months, showing excellent skills in 26 starts. There was some slowdown in September as his velocity tailed off and home runs became a big issue (nine in 36 innings). Duffy enjoyed career-bests in strikeout rate, walk rate, and swinging-strike rate, though some of his control gains with the fastball seemed to come at the expense of his command with the pitch yielding career-worsts in home run rate and hard-contact rate. An excellent slider and changeup hid the declining velocity until September (though his 94.5 mph average in Sept. is nothing to sneeze at). He has a great foundation with premier velocity and two swing-and-miss secondaries. If his finish was more fatigue from a career-high 179.7 innings pitched than the league figuring him out, then there's a lot more success to come. The homer issue preaches some caution, but there's still upside to bid on.

Duffy has been with Kansas City for parts of five seasons with nearly all of his appearances coming as a starting pitcher. In that time, he’s 24-30 with a 3.80 ERA and a 1.36 WHIP, and his strikeout rate has declined each of the previous four seasons. He has done some limited work in the bullpen, and his stuff has looked better in that role than it has as a starting pitcher. Kansas City does not currently have the pitching depth that would allow Duffy to move to the bullpen to help set up Wade Davis in 2016, but that could change in the near future. He’s mostly a fastball/breaking ball type of pitcher and the lack of a good changeup leaves him susceptible to righties, who have hit 40 of the 44 home runs against him in his career. Duffy is endgame material as is, but a potential move to the bullpen reduces his value.

Opportunity knocked for Duffy early in the 2014 season, as a spot in the starting rotation opened up in early May after Bruce Chen hit the disabled list with a bulging disc in his back. The left-handed Duffy took the reins and never looked back, finishing the season with a 9-12 record, 2.53 ERA and 1.11 WHIP. A career-low .239 BABIP may have helped him out a bit, in addition to the fact that he stranded 77.2% of baserunners, but the southpaw was able to provide fantasy utility in most formats nonetheless. Potential fantasy owners may want to exercise caution before reaching too far for Duffy, however, as a 4.42 xFIP suggests that his ERA may be a bit understated, though he'll likely continue to catch breaks in the spacious Kauffman Stadium with an exceptional defensive unit behind him. He threw a career-high 149.1 innings in 2014 (with an extra 4.2 in the postseason), and should expect to surpass that workload in the upcoming year, provided he stays healthy, but keep in mind he did undergo Tommy John surgery once already in June 2012.

Duffy underwent Tommy John surgery early in the 2012 season and finally made it back to the mound for the Royals around the start of the second half last season. However, he made just five starts before landing back on the disabled list with tightness in his forearm. Rather than try to push him into a second return during the 2013 season, the club opted to shut him down for the duration of the year with the assumption that he would be fully rested and rehabbed by the time spring training opened in 2014. Duffy has a solid four-pitch arsenal and high strikeout potential, but command has always seemed to be a bit of an issue. Though he posted a K/BB over 2.50 throughout his time in the minors, he failed to produce one over 1.71 during his 133 innings at the major league level. Of course, that could have also had something to do with his arm troubles leading up to surgery. If all goes well during spring training, he should slot in as the team's third or fourth starter when the regular season begins.

Duffy's 2-2 record with a 3.90 ERA and a 1.6 K/BB through 27.2 innings in 2012 were almost irrelevant as he was plagued with elbow problems early on and eventually shut down at the beginning of May to have Tommy John surgery. He is still in the midst of his recovery and likely won't be ready until some time around midseason in 2013. However, at just 24 years old and loaded with promise, he is obviously a pitcher to monitor when looking for help in the second half. Throughout his time in the minors, he exhibited tremendous strikeout potential, often posting a double-digit K/9 and finishing off hitters with either his 95 mph fastball or an even more impressive looping curve. With the prospect of him coming back to the rotation with his arm even stronger, Duffy could be one of those sneaky second-half sleepers that that can boost a fantasy rotation and lift you up in at least three of the standard pitching categories.

Duffy made his big league debut in 2011, after spending the first month of the season at Triple-A Omaha. A starter, he had 87 strikeouts and 51 walks with a 5.64 ERA over 105.1 innings. Armed with a fastball that sits in the low-to-mid 90s, Duffy struck out over a batter per inning at nearly every stop in the minors, often with good control and command of his pitches. At the major league level he's going to need to rediscover that control as his walk rate was 4.36 BB/9IP in his rookie season. Only 23 years old, Duffy should be snapped up in keeper leagues and by those speculating for strikeouts in deeper leagues.

Duffy made a bizarre departure from the Royals in March to "reassess his life priorities" before returning to the team three months later. Upon his return, Duffy was effective, posting a 2.74 ERA over 62.1 minor-league innings. The Royals plan to give him a chance to pitch his way into the Opening Day rotation this spring, but he's yet to pitch an inning above the Double-A level.

Duffy is a left-handed starting pitcher with outstanding upside. His command and his ability to throw strikes set him apart from most prospects his age. He went 9-3 with a 2.98 ERA in High-A in last season and his 125:41 K:BB ratio over 126.2 innings pitched is excellent. Duffy was selected for the Futures Game and he should be considered an up-and-coming pitcher in the Royals' rotation. He must increase his stamina so he can get deeper than the fifth inning. It is likely he will spend 2010 between Double-A and Triple-A preparing for a debut as a starting pitcher late in the season or in 2011. Duffy should be considered in keeper leagues and is someone to watch very carefully.