Arizona’s dual aces

With 50 games officially in the can, the Arizona Diamondbacks are seated comfortably in second place and only one and a half games out in the National League West. As the Dodgers perpetually underperform and the Padres seem ready to concede, it seems likely that the Diamondbacks could remain on the right side of these standings. Offsetting the recent offensive struggles of Justin Upton, Stephen Drew and Chris Young, both Ryan Roberts and Juan Miranda have been surprising as they move from utility roles to everyday contributors.

But the real anchor of this team has been the top of the rotation, especially its dual aces: Ian Kennedy and Daniel Hudson. Both are performing exceptionally well since coming over from the American League last season.

Kennedy was involved in one of Josh Byrnes’ last major deals during the winter meetings after the 2009 season while Hudson can be seen as one of the few positive trades during the brief Jerry DiPoto reign at last season’s trade deadline. Both pitchers were effectively swapped for other established starters (Kennedy and Edwin Jackson were the main pieces sent off to Arizona in the Curtis Granderson three-teamer, essentially replacing Max Scherzer, while Hudson and David Holmberg were later swapped for Jackson) and have performed well above expectations.

But so far it has been tough to pinpoint who the best starter may be.

Ian Kennedy 74.2 11 7.11 2.29 1.13 3.01 3.12 3.45
Daniel Hudson 66 10 8.18 2.45 1 3.82 2.58 3.34

Held up to wins and losses, Kennedy is far ahead with an All-Star friendly six wins to one loss while Hudson’s five wins and five losses are blemished by an atrocious April that begat an 0-4 start despite solid peripherals and an ERA/FIP differential of 5.64 to 2.94.

So far in May, Hudson has reversed his win and loss record. His strand rate has been a bit fortuitous at 81.7 percent and he has improved his command to bring his ERA and FIP to a closer relationship at 2.27 to 2.29.

In terms of repertoire, both Hudson and Kennedy have a feel for the change-ip and work to establish their fastball early in the count. Kennedy tends to mix in more pitches:

4-seam 2-seam Slider Curve Change
Ian Kennedy 38.4% 20.8% 11.9% 13.9% 15%
Daniel Hudson 61.9% n/a 16.1% n/a 22%

Neither shows a heavy distribution rate of fly balls over ground balls this season, both hovering around 41 to 42 percent in groundball rate. Both have earned reputations early in their careers as being flyball prone, but with Kennedy inducing more infield flies at a rate of 15.2 percent (far above the major league average of 7.4 percent). Hudson has been efficient (or lucky) in keeping the ball in the park.

Ian Kennedy 42% 37.3% 20.8% 15.2% 6.3% .254
Daniel Hudson 41.3% 41.3% 17.5% 10.3% 3.8% .330

Looking at possible regression and improvement, last season Kennedy posted an IFFB rate of 10 percent, but we don’t have enough long term data to know if this is a possible skill (especially with Kennedy’s fly ball tendencies decreasing) or if a large regression is in order. If the latter is the case, then expect that to be one of the reasons for Kennedy’s low BABIP to rise.

Hudson is also well below the major league average with his low home run to flyball ratio, currently just 3.8 percent compared to the 7.1 percent average. It’s tough to spot any trends that could be the cause but it would be fairly impossible for this to continue.


Looking over data supplied by Joe Lefkowitz, we can see that Kennedy has shown an unusual spike in ground balls by way of his curve ball and slider. Let’s break down the movement of these pitches and see if that can tell us anything:

Average Velocity Avg. Horizontal Movement Avg. Vertical Movement #
2010 Slider 83.6 0.29 3.9 208
2011 Slider 85.2 -0.37 4.1 128
2010 Curve 76.6 5.31 -7.94 542
2011 Curve 77 5.35 -7.63 138

In terms of movement, nothing drastic has changed; however, Kennedy has been using his slider a bit more frequently in comparison to last season.

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The payoff of being polite.

Interestingly, Hudson has been inducing more ground balls off his four-seamer compared to his off-speed pitches. For the sake of uniformity, here is Hudson’s PITCHf/x breakdown:

Average Velocity Avg. Horizontal Movement Avg. Vertical Movement #
2010 4-seam 92.5 -7.57 7.76 940
2011 4-seam 93.2 -8.62 6.81 657
2010 slider 84.9 0.58 2.83 143
2011 slider 86.2 -0.78 2.27 177
2010 change 82.7 -10.61 3.03 329
2011 change 83.1 -10.43 3.36 228

Both being right-handed pitchers, neither Kennedy nor Hudson has shown any extreme platoon splits against either right-handed or left-handed opposing batters.

Kennedy career vs. LHH: 675 PA, .223/.297/.372, 2.39 K/BB, 0.83 GB/FB, 3.84 FIP
Hudson career vs. LHH: 338 PA, .235/.315/.349, 2.21 K/BB, 0.64 GB/FB, 3.47 FIP

Hudson does have a better strikeout rate against righties while Kennedy seems to find it easier to strike out lefties. On the groundball side, Hudson gets a better rate against righties while Kennedy gets a few notches more against those standing on the other side of the plate.

Looking at THT Forecasts, our Oliver projection system doesn’t see much regression for either Kennedy or Hudson (although a slight increase in home runs is expected for Hudson). According to projections for the rest of the year, Kennedy profiles for a 4.6 Wins Above Replacement (WAR) while Hudson comes in at 3.5.

So, what does this mean in terms of which one is better? It’s still a difficult decision, as they have different traits. Hudson still relies on his velocity while Kennedy is more of a finesse pitcher. Both do have solid change-ups and mix their off-speed pitches well, but if I had to choose one I would lean toward Hudson, especially with his slight increase in his velocity this year.

Looking at Oliver’s six-year major league equivalent, Hudson is projected to be slightly more valuable in terms of WAR over Kennedy. It’s not by much. Most importantly, the D-Backs have two quality young pitchers to anchor their staff for the next few seasons.

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Kyle S.
Kyle S.

I haven’t seen him pitch yet, but looking at his pitchf/x charts on fangraphs it seems Kennedy’s slider is a slider in name only.

It has all the hallmarks of a quality cutter, and he’s spotting in just the right spots: up and in to lefties and low and away in the strike zone to righties.

Oh, cut fastball, is there any pitcher you can’t make better?