To throw a cutter or cut fastball, you will throw a fastball but get a slight amount of side spin that makes the ball move in or out a few inches.
You do this by moving your fastball grip (usually the 4-seam fastball grip) slightly off-center. Some pitchers bring the thumb slightly up the inside of the ball and the index and middle fingers slightly toward the outside. This gives you a pitch somewhere between a fastball and a slider, and, thrown properly, that's how the pitch will move, like a very tight slider.
For young pitchers, though, there is a tendency to turn the hand too much toward the slider position, getting a "doorknob" action with the hand that can stress the elbow. The pitcher should leave the thumb directly under the ball and move only the fingers slightly left or right, depending on which way you want to cut the ball. As you release it, think "fastball," and spin the ball hard with your middle and index fingers, just as you would the fastball.
If you're a right-handed pitcher holding the ball slightly off- center to the outside part of the ball, the pitch should move a few inches away from a right-handed hitter ... just enough to get it away from the barrel of the bat. Unless you have a fairly high arm angle (throw "over the top") it will be harder to learn to make the ball move the other way, but try it. Just offset the fingers slightly to the inside, and throw with fastball action.
How To Throw A Cutter ... Like Mariano Rivera
To start, you hold it like a fastball. The cutter grip is a little bit off of center. Throwing it is like a fastball, and right here at about the release point, turn over your wrist.
The idea is, it's got fastball rotation, and at about 59 feet, it cuts into a righthander for a lefthanded pitcher. For a righthanded pitcher it cuts into a lefthander.
Why is Mariano Rivera's cutter so good? Because it's so late and so quick, and the rotation has such good fastball rotation. It looks fastball to a hitter because you can't see the rotation.
Additional Information On How To Throw A Cutter
The cut fastball and the sinker have the same goal: to make the hitter hit the ball without getting the meat of the bat on it. Both pitches will be more effective if you first establish the fastball. Then, when you throw the sinker or cutter, the hitter will see what looks like the same fastball arm and hand action, and will not be expecting the ball to move.
Here are a few more cut fastball grips submitted by readers of The Complete Pitcher...
The horseshoe seam of a baseball (side view)
Cut fastball grip (top view)
Cut fastball grip (side view)
Cut fastball grip (top view)
What do you think?
Now it's time to hear from you:
Are there any additional tips that I missed?
Or maybe you have an idea of how I can make this article even better.
Either way, leave a comment and let me know.