Dan Haren's success

According to an interview with the Arizona Republic, Dan Haren largely attributes his success this season to the development of his cut fastball.

"When I got traded over here before last year, I was really working on that pitch," Haren said. "It became a pretty good pitch for me last year, but it's something that I really have leaned on this year. I don't throw 93-94 (mph) anymore. It's more 90-92."

Is Haren right? Are his successes to be attributed to the cut fastball? Let's take a look.

Since Haren was traded, his Cutter usage has increased from 1.6% at 88.4 MPH to 6.6% at 87.8 MPH to 17.5% at 86.5 MPH. Haren has gone from rarely going the cut fastball to utilizing it almost 20% of the time. Over this period, Haren has clearly refined the quality of the pitch, as it has almost quadrupled in runs/100 pitch value from 1.7 to 6.5 in just 3 years. In plain english, this means that Dan Haren's cutter, per ever 100 times it is thrown, has prevented approx. 6.5 runs or garnered the Diamondbacks about two-thirds of a win in value.

Alas, despite the increasing usage/quality of his Cutter, it still is not Dan Haren's best pitch. That pitch still remains, and increasingly is, his fastball. Dan Haren has a sick fastball that, on average, breaks 10.5 inches down and 6.5 inches in on hitters. Such disgusting movement, as one would expect, has led to the best fastball in the majors by a quarter of a win margin (Haren's 18.5 runs/100 pitch value on his fastball is the best in the majors; second is Zack Greinke at 16.3).

So what is to attribute to Haren's successes this season? Let's create a checklist.
1) Sick control. Dan Haren's 7.43 K/BB leads the majors
2) Sick command. Dan Haren's 1.17 BB/9 also leads the majors
3) Improving pitches. This season, Haren's fastball quality has almost doubled in value, while his cutter has continued to improve and his split finger fastball is back to form (from -1.4 runs/100 pitchs to +4.5)
4) A four plus-pitch mix. Each of Dan Haren's four pitches (fastball, cutter, curveball, splitfinger fastball) have positive runs/100 pitch values and good mixture (none is thrown less than 13.8% or more than 48% of the time)
5) A very lucky 84.5 LOB% and .239 BABIP, although the Diamondbacks do have the 8th best defense in baseball right now