What is sneaky

What is “sneaky” movement, like I’ve heard that describe like mike mussina’s fastball and like Chris Youngs but I don’t get what it means

my guess would be quick, late, darting movement. kinda like mariano’s cutter.its hard to read because its hard to see the rotation. it messes with the hitters eyes

realy tight spin and late break where the hitter dont see it coming

I thought sneaky alluded to velocity not movement. It had to do with a guy who did not seem that overpowering, but always seemd to be able to get the ball by you.

This was done by covering the box and hiding the ball well with his motion. Ian.