When discussing Danny Duffy's struggles so far, many people are pointing to a mental thing. Others might be pointing to a mechanical thing. Everyone is pointing at his beard. I'm not going to dismiss those outright, except the beard thing. Beards are popular now, so we all must deal with it. The other things are entirely possible. However, there are some indicators of change that can be found. Some indicators may be reversible.
First, we know that Duffy has troubles with control. He's always run a high walk rate, but that high walk rate has usually been paired with either a high strikeout rate (small-sample 2012 and 2013) or contact management ability (2014). This year, neither of those things is happening, so the control problem is much more of a problem. Duffy has taken the lack of control to greater heights this season. According to Brooks Baseball, Duffy has increased his percentage of pitches thrown outside the strike zone by 7 percentage points (55.9 percent to 62.9 percent).
It's worth noting that Fangraphs' PitchF/X data and their other pitch data don't have Duffy increasing or decreasing his rate of pitches within the zone. Differing methods of quantifying the strike zone could be the culprit. I think this lends credence to the idea that Duffy is nibbling around the edges of the zone. The absolute strikes and balls should be the same with all systems; it's the borderline pitches that might be classified as in zone or out of zone depending on how the strike zone is drawn.
Because of the general lack of control, Duffy has not been able to get first pitch strikes as well as he did last year. That rate has decreased from 59.1 percent to 56.7 percent. Yet, Duffy has not actually spent a greater portion of his time behind in the count. I counted the number of pitches Duffy has thrown behind in the count compared to ahead in the count (from Brooks Baseball), and the ratio is about 1:1 in both 2014 and 2015. That means, more or less, that Duffy has probably done a good job of battling back into counts this year. That comes at a cost.
See, Duffy gets very predictable when he's behind in the count. In 2015, against lefties, he throws 86 percent hard stuff; against righties, he throws 70 percent hard stuff. These are actually DECREASES from 2014, which could reflect a desire to become more unpredictable. Like I said earlier though, Duffy has more of a control problem than he has had in the past. He is having a tougher time throwing his breaking and offspeed stuff for strikes, so hitters can sit fastball when they are ahead in the count. When hitters are sitting fastball, they can hit the fastball.
This has led to a certain result. Baseball Reference contains split data that allows us to see production allowed while the batter is ahead and while the pitcher is ahead. In 2014, Duffy allowed an OPS 52% better than MLB average last year while behind in the count. Hitters just didn't perform well even when they were ahead last year. I have no idea if allowing lower than average production while behind in the count is a skill for pitchers. I suspect not. In 2015, Duffy has allowed an OPS 19% worse than average while behind in the count. Either luck, strategy, or both have bitten Duffy, and his fastball is the one that's getting crushed the most.
In order to improve, Duffy should really focus on getting the first-pitch strike. He still holds batters to abysmal production when he gets ahead in the count. There is a strategy change that Duffy can employ in this space. Last year on the first pitch, Duffy threw his four seamer 79 percent of the time against lefties and 55 percent of the time against righties. His four seamer is the pitch he can throw for strikes the best. In 2015, those percentages have decreased to 69 percent and 34 percent, respectively. The sinker and slider have increased dramatically, but those are less effective pitches. Hitters whiff a bit more on the sinker, but when they do make contact it's much stronger. Duffy can't locate the slider as well as the fastball, which leads to him falling farther behind in the count.
Having said that, it's possible that this is all part of the cat-and-mouse game of adjustments. Perhaps Duffy and the Royals thought that he was too predictable last year, and hitters would adjust this year. Maybe they thought that hitters would be teeing off even more than they are now if he remained that predictable. That may be true, but hitters are definitely teeing off with the current strategy. It's time for something to change.