The Spin On Bailey’s Fastball

Andrew Bailey‘s four seam fastball is a remarkable pitch. At 2693 RPM, it leads all major league fastballs in spin rate. To quote directly from the Statcast glossary on the benefits of increased spin on a pitch:

“As more data have become available, most experts have agreed that fastballs and breaking balls are tougher to hit when they possess higher Spin Rates. In fact, some data suggest that Spin Rate correlates more closely than Velocity to swinging-strike percentage.”

The results that Bailey has received from his fastball attest to this statement. While major league pitchers average around a 7% swinging strike rate on the four seam fastball, Bailey has gotten whiffs at a 15.7% clip this year.  And when batters have put the pitch in play, the resultant exit velocity is on par with that against Clayton Kershaw‘s fastball.

Spin rate influences the movement on a pitch, and prior to Bailey’s shoulder surgery, most of the movement on his fastball was in the vertical direction. The 11 inches of “rise” on his four seamer ranked among the highest in the league from 2009-2013. But following his surgery, the pitch started to evolve.

Velocity (mph) Horizontal Movement Vertical Movement
2009-2013 94.9 -1.6 11.1
2015 93.4 0.7 10.6
2016 92.6 1.8 9.3

The 2016 version of the pitch is still being classified as a four seam fastball, but a more accurate description of the pitch would be a cut fastball. The difference is in the horizontal movement. Instead of running almost two inches to his arm side, the pitch is cutting almost two inches to his glove side. It doesn’t look like much, but that’s a difference of almost 4 inches, and now the movement and velocity closely resemble one of the best pitches in baseball.

Velocity (mph) Horizontal Movement Vertical Movement
Kenley Jansen 93.5 2.2 9.7
Andrew Bailey 92.6 1.8 9.3

Kenley Jansen has spent the last six years dominating hitters with this cut fastball. He throws the pitch almost exclusively, only mixing in a slider an average of once every ten pitches. He’s ridden this formula to a career 13.7 strikeouts per nine innings and 2.23 ERA (2.01 FIP), ranking him among the best relievers in the league over the last ten years. But the most impressive of these numbers, and the most pertinent to Bailey, might be the fact that he gets these results throwing his cut fastball almost 90% of the time.

The reason the pitch can be used at such a high frequency without losing effectiveness is the deceptive movement on the pitch. Baseball physics expert Alan Nathan described the concept in a short but informative article at Baseball Prospectus, using Mariano Rivera‘s cutter as an example. A brief excerpt from that piece:

“I’m not sure I really have much to say about the subject of late break. What I do have to say is summarized in the figure below (click to expand), showing Mariano Rivera throwing his cutter.

The solid curve is the actual trajectory, taken from PITCHf/x data. The dotted curve is a straight line projected from the release direction. The two curves look pretty nearly identical until about 20 feet from home plate, which is just about the point of no return for the batter. The ball deviates from the straight-line path at that point and ends up with about 0.5 feet (6″) of movement, so the pitch that looks like it might hit the corner ends up 6″ off the plate (and breaks the bat of a left-handed hitter, a rather common occurrence for Mo).”

In addition to confounding hitters with this perceived late break, Bailey and Jansen both put enough spin on the ball to create above average “rise” on the fastball. The combination of the two factors makes it an incredibly difficult pitch to square up. As a result, Bailey gets more missed barrels and empty swings on this fastball than any one of his secondary pitches.

Bailey might benefit from following a similar blueprint to Jansen and increasing the use of this pitch. His sole issue this year has been giving up too many free passes, and the problem stems from the fact that opposing hitters are just not chasing his pitches, specifically his breaking pitches, out of the strike zone. The sample is small, but the rate of swings on his out of zone pitches is the lowest of his career.

MLB 2016 28.5
Bailey Career 28.8
Bailey 2016 17.8

Batters are laying off his secondary pitches, leading to more called balls and less swinging strikes. All told, hitters are missing on his breaking pitches at less than half the rate of his fastball. The primary purpose of the non-fastball offerings is to disturb a hitter’s timing, inducing whiffs and weak contact.  If Bailey is failing to accomplish this with his secondary stuff, he would be better served sticking with what does induce whiffs and weak contact: an almost unhittable fastball with tremendous spin.



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  1. Romus

    June 02, 2016 03:23 PM

    Curious ……is there a device that can actually calculate the spin rate?

    • Alan Nathan

      June 02, 2016 03:44 PM

      The Trackman radar device, which is an integral part of the Statcast system in all MLB parks, measures the spin on the pitch. However, I don’t think the data are public (but I may be wrong about that).

      • Romus

        June 02, 2016 03:56 PM

        Ok..thanks for that information

  2. Francisco (FC)

    June 03, 2016 01:27 PM

    I always wonder… how aware are front offices and coaching staffs of these things? Whose job is it look at the data and make suggestions? (i.e. “Andy, why don’t you throw your fastball a lot more? You’re not fooling anyone with those breaking pitches.”)

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