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Yesterday’s Dancing Knuckleball

Yesterday, knuckleballer Charlie Haeger had a pretty amazing game. He struck out 12 batters while walking four in six innings. He also threw three wild pitches, two of which were on third strikes and got far enough from A.J. Ellis for the batter to reach.

Obviously, based on the 12 strikeouts, Ellis wasn’t the only one having a tough time with Haeger’s knuckler. By my count he threw 94 knuckleballs (along with 22 fastballs) with 43 swings and 13 whiffs. That works out to a 70% contact rate and a 13.8% swinging strike percentage. Both those rates are very good. That contact rate was about where Huston Street and Andrew Bailey were all of last year (not to say that Haeger will maintain such a rate, but just to put it in context). Haeger’s knuckleball was dancing like crazy.

I have talked about the knuckleball before, but here’s a quick refresher. While all other pitch types have consistent movement — fastballs rise and move towards the glove-side, curves drop and move away from the glove-side — and cluster out cleanly in horizontal movement versus vertical movement space, the knuckleball has no clear movement and instead forms a diffuse cloud when plotted in horizontal movement versus vertical movement space. Some move up-and-in, others up-and-away, others down-and-in, and others don’t move much at all. Not surprisingly, the success of a knuckleball is directly tied to this amount of movement. Those which move little are rarely whiffed and hit hard. Those that move far result in whiffs and weak contact. Tim Wakefield is successful because his knuckles have a large spread in movement.

With that in mind I wanted to see whether Haeger’s knuckleballs yesterday had more movement than they did in his previous appearances. Here are the fraction of Haeger’s knuckleballs whose movement fell in one of three categories (movement measured as the square root of the sum of the square horizontal movement and square of vertical movement). I included the value from yesterday, his career and the value for Wakefield’s knuckleballs.

                   Haeger          Wakefield
               Career  Yesterday    Career
0-5  inches      0.35      0.32      0.32   
5-10 inches      0.53      0.50      0.48
10+  inches      0.12      0.18      0.20

Haeger’s knuckleball was moving a lot more than previously in his career, though still not as much as Wakefield has averaged through his career. Obviously this one value does not tell you everything, but I think it is a nice metric to show us that his knuckleballs were really moving yesterday — that is if the 12 strikeouts wasn’t enough.