Learning how to throw a knuckleball is one of the most complicated tasks in sports. There are only a handful of pitchers who know how, and few are willing to share.

So here's a link for all you future knuckleballers to bookmark. Mets pitcher R.A. Dickey, an All-Star who is tops in the National League with a .93 WHIP through the first half of the season, demonstrated how to throw a knuckleball during an appearance on "The Late Show" on Wednesday.

Dickey told host David Letterman that he digs his pointer and middle finger behind the "horseshoe" of the baseball and he balances the ball with his thumb and his index finger. He keeps his wrist at a 90 degree angle and lets go "at the opportune moment." Dickey said when he throws a good pitch, it feels like it "pops" out of his hand.

Later in the show, Letterman even put on a catchers mitt and caught a few of Dickey's knuckleballs.

Apparently, it's not easy to catch a knuckleball. So if Dickey ever needs a replacement catcher in New York, maybe he can give Letterman a call.

-- Follow Robbie Levin on Twitter @RobbieLevin.

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