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@22and25 posted:

Spin efficiency is a measure of how much the spin of the ball contributes to movement. You would want a very low spin efficiency on knuckleball as spin, and the resulting movement caused by spin, will kill the erratic movement associated with the uneven forces pushing a knuckle ball around as it travels.

Would this be a good reading then:


They labeled everything fastballs so I can’t tell which are curves, changes, or knuckles. The 45 is true spin and 2.9 is efficiency, so I’m guessing that is a knuckle compared to other pitches ranging from 1900-2200. He has a few others at 120-130 but they have higher efficiency scores. We saw a site and can’t find it now that said an MLB knuckle would average 150 or lower at 74mph

Cut and paste form a Driveline article I found online:

“If you’re practicing on a Rapsodo device, the most important metric to monitor will be spin rate. We want to aim as close to 0 and 100 RPMs as possible. This means that throughout a ball’s flight, it should rotate at most 1.5-2 times. Anything above that and you might be limiting the pitch’s ability to move erratically, as a great knuckleball would.“

I would think your eyeballs would be better, or how hitters react, or at least go along with rapsodo data.

Trackman will track the ball from the hand to the termination of the pitch.  Rapsodo gets a short set of data points at release and then applies an algorithm to determine the metrics.  Something with such low spin as a knuckleball gives me doubt on the results.

All opinions are mine and mine alone. I would hate to derail a future knuckleballer's success. It's good to have at least one knuckleballer around.  Makes goofy lefthanders look like normal people.

66 MPH with 1500 spin and a -1.9 in break does not seem like a knuckle ball.

I know. I'm trying to figure out the Rapsodo data but it is all over the place. Everything was labeled fastball. HIs curve is usually in the 70's and same with the change. Even his knuckle is usually 68-70. He threw about 6 total; 1 tumbler, 4 very good ones, and 1 that got a "filthy" from one of the coaches (he also later asked my son one on one about it and said he throws it very well). What does the 45 "true spin" mean?

@Go44dad posted:

Go to youtube and look at videos posted by Simple Sabermetrics. Look at his content for explanations. Short, simple videos. Here’s the basic Rapsodo video.

Thank you. That was helpful. So here’s another twist to add to this... the Rapsodo cloud account was set up by the showcase. When my son clicked the link to open it there was another kid’s name there and he said he changed it once he confirmed the account. Guess I have no idea if these pitches were his or another kid.

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