Difference between Knuckleball and Knuckler

What is the difference between Knuckleball and Knuckler?

Knuckleball as a noun is a pitch thrown with the ball gripped on the fingertips and released with no rotation which travels over an unpredictable path to the plate due to micro-turbulence in the air. while Knuckler as a noun is a knuckleball

We hope you now know whether to use Knuckleball or Knuckler in your sentence.