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The Cubs vs. Steven Wright: Knuckleball 101

Or why I’ll be checking the weather at Fenway all day.

Steven Wright throwing a knuckleball in 2015
Winslow Townson-USA TODAY Sports

Since 2010 there have only been three active knuckleball pitchers* in the major leagues so it’s not totally surprising that in facing Steven Wright today the Cubs will face a knuckleballer for the first time since 2011. What is a little surprising is that the last time the Cubs faced a knuckleballer (R.A. Dickey on May 26, 2011) it was the second knuckleballer they’d seen in a week (they faced Tim Wakefield at Fenway on May 22, 2011).

The Cubs did next to nothing against the knuckleball in either outing. While they won the game against the Mets, all of their runs came after Dickey left with an injury in the third inning. They took the loss against Wakefield who held them to one run on four hits over 6⅔ innings.

I was lucky enough to see Wakefield pitch in person three times when I lived in Boston, including the above game against the Cubs. Having seen the knuckleball in action a few times I am filled with excitement and dread for today’s game. The knuckleball, you see, is sorcery. Simultaneously the best and worst of possible pitches, and I’m curious to see which pitch Steven Wright will bring to today’s game.

Before I go further, I mean, look at this pitch from Wright [VIDEO].

This is not even a catchable pitch, let alone a hittable pitch. The laws of physics appear to have changed for that pitch. Chris Davis has no chance on that pitch, and neither does anyone else. You throw iterations of that pitch over the course of nine innings and you will win a lot of ballgames because the human brain can’t predict where the ball will be from one moment to the next.

But this is sorcery, so there is a cost to being able to throw that pitch and the cost is this: it doesn’t always work the way it’s supposed to and when a knuckleball isn’t knuckling it’s basically batting practice.

What I’m trying to say is we are either hitting nothing or everything today, so I thought it might be worth trying to figure out which is more likely (you know, taking into account predictable things and not wizardry).

Whenever Wakefield would start in Boston the first thing we’d do is look at the weather. Dry and cold was a good sign. Too wet was a bad sign. Too hot and dry was a bad sign. Hot and humid had a chance. In fact, if you look up weather and the knuckleball you find a lot of pieces like this: Weather and Wright’s Knuckleball or Cold Weather and the Knuckleball. The knuckleball works best when there is no spin on the ball — the ball spins less in dense, colder, air. It is not an accident that the most recent successful knuckleballers have spent their time in Boston, Minnesota and Toronto.

Here’s a more technical explanation:

Why the motion: ideally, a knuckleball from the pitcher to the plate will do only one half spin, moving the seams that held them into the side (90 degrees). The drag (air resistance) of the seams (which increases relatively by the lower velocity of the ball towards the plate than traditional pitches) will cause the ball to have an increased sideways movement, thus "flutter". The argument against the wind is that a lateral (side to side) wind, would exaggerate the natural lateral movement of the knuckleball, making it more "wild".

That's what throwing a knuckleball is all about. How about the temperature effects? Higher temperature decreases the density of air molecules and low temperature increases their density. When it is cold and the air molecules are denser, this has two effects: a. it slows the velocity of the ball which, in turn, b. decreases the spin of the ball, thus making a knuckleball, flutter better. Here is an extreme example to make it clearer: Cold increases water molecule density. Is it easier to push your finger through liquid water, or through ice? The same principle applies to the air.

It gets even crazier, as this incredibly thorough examination of the physics of the knuckleball points out. The knuckleball is a pitch that, at its best, basically takes advantage of its lack of speed and the physics created by the seams on the ball to minimize the spin of the ball and maximize its movement due to wind. That movement is fundamentally unpredictable, and results in at bats like Davis’ above. If you’re going to click through on one link in this post, make it the one above - I still think this pitch is wizardry, but wizardry based on pretty advanced understandings of physics is pretty cool.

I have no hard figures, but it seems that a thrown ball begins to react to the wind at speeds around 50 mph or so. Non-rotating balls thrown at, say 90, have much less time to move much. The tradeoff seems to be around 70 mph, fast enough for some Little Leaguers to try their hand at one at major-league distances. You can see how helpful it may be to intentionally change speeds on your knuckleballs. Throwing some in the high 70s and low 80s will cause them to move little, but they'll still likely shudder and shake enough to knock that very small sweet spot off-line enough to make a clean hit all the harder. However, if it doesn't move at all, it's essentially a BP fastball,which may make it all-too easy to hit deep. If you have an insufficient number of them sinking the way you want (sinking being the best way to miss the bat) your option's there to change velocity of each pitch on your own, further adding to the batter's confusion. There is something to be said for having the command of the knuckleball so as to produce a lot of strikes and produce enough difference from one to another to have a good day on the mound, whether the ball does it all on its own, or if you have some say in what it does.

It has been found, though, that if the ball rotates slightly clockwise or counter-clockwise and the stitches are aligned properly from the start, there may be some lift produced to follow, producing a ball that actually corkscrews! I've thrown them-- tough to do all the time, to say the least. This may be what Hoyt Wilhelm called it his "spinner". It rotates about an off-center axis pointing generally towards the plate, gradually sinking on the way in, making it relatively easy to catch and to throw for strikes but completely unhittable except with blind luck.

This pitch is so fascinating that there is an excellent documentary devoted solely to the knuckleball. Knuckleball! is absolutely worth 93 minutes of your time, and if you have the time before the game today, it will certainly make Wright’s start even more enjoyable.

In case you were wondering, here is the Accuweather forecast for Fenway Park today. As of this writing, game time should be 75-80 degrees with the humidity clearing out earlier in the day and a west-northwest wind around 13 miles per hour. That lack of humidity and increased heat might change the air density enough to keep the knuckleball from knuckling, or we may see the pitch that Willie Stargell called a “butterfly with hiccups.”

Either way, I’m excited to see what brand of pitching wizardry we encounter this afternoon at Fenway.

*For the purposes of this post “knuckleball pitcher” refers to pitchers who primarily rely on the knuckleball, not pitchers who have ever thrown one ever. I used this list and Wikipedia to determine active knuckleballers.