Knuckleballs and Grounders

News out of the Red Sox camp (h/t Neyer) is that the Red Sox might finally part ways with Tim Wakefield. The season is still is ways off, so there is time for injuries to come up and Wakefield find a way into the rotation. But if this is the end of the line for Wakefield with the Red Sox — only seven wins shy of 200 and 13 away from the franchise record — it would be too bad. For one thing, last year was a rare one when two knuckleballers got a substantial number of innings: Wakefield and R.A. Dickey.

Looking at the two pitchers’ numbers I was struck by their very different ground-ball rates, 55% for Dickey versus just 37% for Wakefield. My main frame of reference for a knuckleballer has been Tim Wakefield, so l always assumed that there was something about the knuckleball which led to lots of fly balls. But with Dickey’s high ground-ball rate maybe it is just Wakefield’s knuckleball.

The most likely culprit with differences in ground-ball rates is pitch height. So here, on the left, are histograms of knuckleball height for the two pitchers. On the right is ground-ball rate by knuckleball height.

So, yeah, Dickey’s knuckleballs are a little bit lower in the zone than Wakefield’s. But that alone is not enough to account for the difference: no matter the height Dickey’s knuckleballs get more grounders than Wakefield’s.

Looking elsewhere, the big difference between the two pitches is that Dickey’s is about 10 mph faster: averaging 76 mph versus 66 mph for Wakefield. It looks like this plays a big part in the difference between the ground-ball rates:

For the 65-70mph range where they both throw knuckleballs (though Dickey rarely and mostly earlier in his career) they get roughly the same ground-ball rate. But once Dickey’s knuckleballs get up to the mid-70s they get tons of grounders. It seems the additional speed on Dickey’s knuckleballs don’t lead to any more whiffs (whiff rate on Dickey’s knuckleballs in 8.2% compared to 8.4% for Wakefield), but rather more ground balls.

Having two knuckleballers gives a nice opportunity to compare what is the case about knuckleballs generally versus what is unique to specific pitchers. I personally hope that Wakefield finds a way to stick around for 2011.

Quick note: Garik16 has a great three part series on the knuckle ball that looks at both Wakefield and Dickey. Part 1. Part 2. Part 3.

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Dave Allen's other baseball work can be found at Baseball Analysts.

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