He’s Baseball’s Only Mud Supplier. It’s a Job He May Soon Lose.

This particular mud, hauled in buckets by one man from a secret spot along a New Jersey riverbank, is singular in its ability to cut the slippery sheen of a new baseball and provide a firm grip for the pitcher hurling it at life-threatening speed toward another human standing just 60 feet and six inches away.

Tubs of the substance are found at every major league ballpark. It is rubbed into every one of the 144 to 180 balls used in every one of the 2,430 major league games played in a season, as well as those played in the postseason. The mudding of a “pearl” — a pristine ball right out of the box — has been baseball custom for most of the last century, ever since a journeyman named Lena Blackburne presented the mud as an alternative to tobacco spit and infield dirt, which tended to turn the ball into an overripe plum.

Glen Caplin, an M.L.B. spokesman, said that “pre-tack baseballs” are continuing to be tested in the minor leagues. But the reviews have been mixed.

“If you change one property of a baseball, you sacrifice something,” Caplin said. “The sound off the bat was different. The ball felt softer. The bar to change a ball is very high.”