Fantasy Baseball: Danny Duffy is the most interesting pitcher in baseball right now

Danny Duffy looked like he was making the leap to stardom last season with the Royals. After a rocky start to his career, defined as much by injuries and under-performance as the talent he showed, Duffy seemed to figure things out.

His 3.51 ERA wasn't the best he's ever managed, but an increase in strikeout rate and improved control made it look much more promising than even his 2.53 ERA in 2014 did. He had a 19-start stretch with 126 strikeouts in 120 2/3 innings, with a 2.61 ERA to go with it, before running out of steam in August and September. Given that he started the season in the bullpen, it was fair to assume he just ran out of gas, and would be better suited to handle a starting role full-time after a full offseason of preparation.

Danny Duffy SP / Kansas City

And, so far, so good. He's gone at least six innings in each of his first four starts, sporting a 1.32 ERA and 1.02 WHIP. For someone who showed ace potential last season and was drafted for that potential upside as the No. 22 starting pitcher off the board, this is exactly the kind of start you wanted to see. The results are certainly ace-caliber, but if you dig a little deeper, there are signs of trouble.

To start with, after striking out 25.7 percent of opposing hitters last season, Duffy has seen that number dip to 21.2 percent. That's a bit below average for the league as a whole, and he has combined that with a 9.6 percent walk rate, a huge regression from last year's career-best 5.8 percent rate. Both are more in line with Duffy's middling career numbers than the ace-caliber ones he put together, and combine with his flyball tendencies to make for shaky peripherals.

For example, last season, Duffy had a 20.0 K% minus BB%, good for eighth in the majors. His current 11.5 mark would have ranked just 57th among qualified starts. The 19 pitchers who were between 13.0 and 10.0 in this number last season averaged a 3.98 ERA, and the outliers were groundball pitchers like Carlos Martinez, Tanner Roark and Aaron Sanchez. Combining flyball tendencies with an above average walk rate and only average strikeout numbers is usually a combination that leads to middling results, but that hasn't been the case for Duffy so far.

Add on the fact that preseason concerns about Duffy's diminished velocity have come to fruition, and it's not unreasonable to be concerned about Duffy sustaining this performance. The top-line numbers suggest an ace, but there is a lot here that screams regression, and it could make Duffy the ultimate sell-high candidate of the season's first month.

There are complicating factors here. For one, although Duffy's velocity is down, he isn't exactly oblivious to it. He started throwing his two-seam fastball more last season, and he has continued that trend in the early going. You tend to trade whiffs for groundballs when you trade your four-seamer for a two-seamer, and that's not a bad tradeoff to make if you can't blow the ball past batters.

However, what might be more interesting -- and telling -- is that Duffy's overall fastball usage is down pretty significantly. He threw his two fastballs 59.4 percent of the time last season, a number that is down to 47.0 through his first four starts. This is something we typically see from older pitchers, and it could be an acknowledgment by Duffy that his fastball can't be his dominant pitch anymore.

Luckily, his slider and changeup have been extremely sharp in the early going, with swinging strike rates of 20.7 and 21.3 percent after around 100 pitches thrown for each. An increased reliance on his secondary stuff has helped Duffy up his swinging strike rate from 12.9 to 15.1 percent, an elite mark.

That it hasn't translated to strikeouts yet is curious, but it could be a sign that Duffy's early-season peripherals aren't necessarily worth worrying about. Swinging strike rate might actually be more predictive early on than strikeout rate, because you're looking at several hundred pitches, vs. just 104 total batters faced. When Duffy has two strikes on a batter, he has finished just 38.6 percent of those plate appearances with a strikeout, compared to 49.9 percent last season. The difference there -- about six strikeouts  to date -- represents most of the difference between this year's strikeout rate and last year's, and it could be explained away at least in part by randomness.

Duffy is definitely a different pitcher this year than he was during his breakout last season. His velocity is down, his pitch selection has changed, and his results are wildly divergent. Whether it is a good or bad thing remains to be seen, but there is certainly evidence here for both sides of the argument.

If I could flip Duffy right now for an ace, especially a struggling one like Corey Kluber or Justin Verlander, I wouldn't hesitate to do so. However, Duffy still has ace potential of his own, and I wouldn't just trade him to trade him. If his per-plate appearance numbers catch up to his per-pitch numbers, Duffy still has room to grow. No matter what, Duffy's season isn't what it seems so far. 

Fantasy Writer

Though he can be found covering three different sports depending on the time of year, there is one unifying theme in how Chris Towers approaches sports; "Where's the evidence?" It doesn't matter how outlandish... Full Bio

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