Pitchers rub the baseball to improve their grip. A brand-new baseball comes out of its wrapper with a slick, glossy finish that makes it surprisingly hard to control, so every ball used in a professional game is rubbed down beforehand to remove that factory sheen. During a game, pitchers also rub the ball between pitches to maintain a consistent feel, working the leather with their fingers to keep the surface from becoming too smooth or too wet.
The Problem With a New Baseball
Baseballs straight from the factory are coated in a thin layer of gloss, wax, and slimy residue from the manufacturing process. That coating makes the leather feel almost waxy, and pitchers describe new balls as dangerously slippery. The friction between a pitcher’s fingertips and the ball directly affects spin rate, accuracy, and the ability to locate pitches. When that friction drops, control suffers, and an errant pitch at 95 mph poses a real safety risk to batters.
This isn’t just anecdotal. Research published in Nature measured the sliding friction between fingertips and baseballs from different leagues. Major League baseballs showed 15 to 25 percent lower friction coefficients than balls used in Japan’s Nippon Professional Baseball league. Japanese pitchers who moved to MLB teams consistently reported struggling with how slippery the American balls felt. Yu Darvish publicly stated that the slipperiness of MLB balls is a key reason pitchers resorted to using unauthorized sticky substances.
What Happens Before the Game: Rubbing Mud
Every baseball used in an MLB game gets rubbed with a special mud before it ever reaches the field. The official rules require umpires to inspect each ball and confirm “the gloss is removed.” This pre-game rubbing is done by clubhouse staff using Lena Blackburne Baseball Rubbing Mud, a product harvested by the Bintliff family from an undisclosed spot along the Delaware River for nearly 90 years.
The mud works through three mechanisms that engineers at Penn have studied closely. First, it fills in the microscopic pores of new leather, eliminating slick spots by laying down a thin, cohesive film. Second, the clay-rich film makes the surface slightly tacky, roughly doubling the grip between a finger and the ball. Third, a sparse sprinkle of tiny sand grains in the mud gets glued to the leather by the clay, creating what researchers describe as “miniature cleats” on the ball’s surface that boost friction. The result, as one researcher put it, is a material that “spreads like a skin cream but grips like sandpaper.”
At least one dozen reserve balls must be available at every game, and all of them go through this process. It’s one of baseball’s quieter rituals, but it touches every single pitch thrown in the major leagues.
Why Pitchers Keep Rubbing During the Game
Even after the mud treatment, a baseball’s surface changes with use. Dirt, sweat, moisture, and the oils from players’ hands all alter how the leather feels. Pitchers rub the ball between pitches for several practical reasons: to work off excess moisture, to redistribute dirt evenly across the surface, and to re-familiarize their fingers with the seams and texture. It’s also partly habitual, a rhythmic part of the pitcher’s routine that helps them reset mentally between pitches.
Pitchers are also allowed to use a rosin bag, a small cloth pouch filled with pine resin powder that sits behind the mound. Rosin absorbs moisture from sweaty hands and adds a slight tackiness to the fingertips. What pitchers cannot do, per the rules, is intentionally alter the ball with soil, sandpaper, paraffin, or any other foreign substance. The line between legal grip maintenance and illegal ball doctoring has been a source of controversy for decades.
How Grip Affects Pitch Performance
The connection between friction and pitching effectiveness is measurable. In a study of semiprofessional pitchers throwing four-seam fastballs, researchers compared pitches thrown under low-friction conditions (wet fingertips) versus high-friction conditions (rosin-treated fingertips). When friction dropped, the ball slipped more against the fingers at release, directly reducing spin rate. Higher spin rates make fastballs appear to rise and breaking balls snap more sharply, so even small changes in grip can meaningfully alter how a pitch moves through the strike zone.
Friction also affects accuracy. The force at the moment of release determines the ball’s trajectory, and when a pitcher can’t predict exactly how the ball will leave their hand, their ability to hit specific spots in the zone degrades. This is why pitchers are so particular about ball feel. A slight change in surface texture can be the difference between a pitch that catches the corner and one that drifts over the middle of the plate.
The Sticky Substance Controversy
Because MLB baseballs are slipperier than those used in other professional leagues, many pitchers have sought extra grip beyond what mud and rosin provide. For years, the use of sticky substances like pine tar, sunscreen mixed with rosin, and commercial grip enhancers was an open secret. MLB began cracking down with on-field inspections in 2021, but the underlying problem remains: the standard baseball is hard to grip consistently, especially in cold or humid conditions.
MLB has been working on a longer-term solution. The league partnered with Dow Chemical to develop a pre-tacked baseball that comes out of the wrapper with a built-in grip coating. A prototype was tested in Double-A in 2023, and players reportedly loved the improved feel. But in hot weather, the coating became too gummy, highlighting how difficult it is to engineer a surface that works across all conditions. According to former pitcher CC Sabathia, now an MLB advisor, roughly 15 PhDs are working on the problem. For now, though, rubbing mud remains the standard.
How Other Leagues Handle It
Japan’s NPB uses sand rather than mud to prepare its baseballs, and the resulting surface has measurably higher friction than MLB balls. That difference is significant enough that pitchers moving between leagues notice it immediately. The balls themselves are also manufactured differently, with a slightly different leather texture that contributes to the grip gap. It’s a reminder that “rubbing the ball” isn’t unique to American baseball. Every professional league has some version of the practice, because the core problem is universal: raw manufactured baseballs are too slick to throw with precision at competitive speeds.