Umpires check pitchers’ hands to look for sticky foreign substances that would give them an unfair advantage over hitters. Since June 2021, MLB has required umpires to inspect every pitcher’s hands multiple times per game, whether or not anyone suspects cheating. The checks are quick, routine, and visible enough that you’ve probably noticed them during a broadcast.
What Sticky Substances Actually Do
A pitcher’s ability to spin the ball is everything. More spin means more movement, and more movement means the ball curves, drops, or rises in ways that make it dramatically harder to hit. This is thanks to a physics principle called the Magnus Effect: a spinning ball creates uneven air pressure around itself, which pushes it off a straight path. The faster the spin, the sharper the movement.
Sticky substances applied to the fingers let a pitcher grip the ball more tightly at the moment of release, which increases the spin rate. Even a small boost in spin can turn a hittable fastball into one that seems to jump out of the strike zone. Over the past decade, pitchers increasingly turned to specially engineered adhesives (often called “sticky stuff”) that could add hundreds of revolutions per minute to a pitch. By 2021, the problem was widespread enough that MLB stepped in with aggressive enforcement.
The Rules Behind the Checks
Two longstanding rules form the basis for the inspections. Rule 3.01 prohibits any player from altering the ball with soil, rosin, paraffin, sandpaper, or any other foreign substance. Rule 6.02(c) goes further for pitchers specifically: they cannot apply a foreign substance to the ball, deface it, or even have a foreign substance on their person or in their possession. That includes things like tape, bandages, or anything attached to the hand, fingers, or wrist.
The only legal grip aid is the rosin bag that sits behind the mound. Rosin provides a light, dry tackiness that absorbs moisture. But pitchers cannot mix rosin with other substances, like sunscreen, to create extra stickiness. Before each game, clubs must submit their rosin bag along with the game balls for umpire review to ensure nothing has been tampered with.
What Umpires Look For
Umpires inspect the top and bottom of the pitching hand, focusing on the thumb, index finger, middle finger, and palm. They’re feeling for stickiness that goes beyond what rosin or sweat would produce. If a pitcher’s hand is, in the league’s own words, “unquestionably sticky,” the umpire concludes a foreign substance was used and issues penalties.
Umpires also have discretion to inspect any part of a pitcher’s uniform, including the glove, hat, and belt. In recent seasons, the emphasis has shifted more toward the hands and fingers themselves, since that’s where substances are most likely to end up at the point of release. Catchers and even position players can also be checked if circumstances warrant it.
When and How Often Checks Happen
The timing is designed to avoid slowing the game down. Inspections typically happen between innings or during pitching changes. Starting pitchers will usually be checked more than once per game. Relief pitchers are checked when they enter the game or at the end of their first inning.
Umpires have been instructed to be unpredictable in their timing and scope so pitchers can’t simply wipe their hands clean before an expected check. If an umpire sees a pitcher wiping off his hands before an inspection, that alone can result in an immediate ejection for attempting to conceal a foreign substance. Opposing managers can also request an inspection at any time if they spot suspicious behavior on the field, though the check won’t happen until the current at-bat finishes.
What Happens If a Pitcher Gets Caught
The penalties are straightforward and immediate. A pitcher found with a foreign substance is ejected from the game and automatically suspended. The suspension follows past precedent, typically 10 games for a first offense. The pitcher’s team has to continue without him for the rest of that game, and the suspension means missing additional starts afterward. There is no warning system. One violation triggers the full penalty.
This zero-tolerance approach was a deliberate shift. Before 2021, the rules technically existed but enforcement was lax. Umpires rarely checked unless an opposing manager made a formal request, which was considered a confrontational move and almost never happened. The 2021 crackdown changed the dynamic entirely by making checks routine and mandatory for every pitcher in every game.
The Grip and Injury Debate
One argument pitchers have made in favor of grip substances is safety. The logic goes like this: a better grip means less strain on the elbow and shoulder because the pitcher doesn’t have to squeeze as hard to control the ball. Some pitchers believe stronger grip reduces stress on the ulnar collateral ligament (the tissue on the inner elbow that’s repaired in Tommy John surgery).
The science doesn’t fully support this. Research on pitchers found that grip strength has no significant correlation with the amount of stress placed on the inner elbow joint during repetitive throwing. After 100 pitches, the elbow showed similar levels of joint-space widening regardless of how strong the pitcher’s grip was. The forearm muscles involved in gripping may not meaningfully reduce the tensile stress on the ligament during the violent act of throwing. So while the safety argument is popular among players, the biomechanical evidence suggests that grip alone isn’t protecting the elbow the way many assume.
Why You See It Every Game Now
The hand checks you see on broadcasts aren’t random or accusatory. They’re a standardized part of every game, applied equally to both teams. The goal is consistency: by checking everyone, the league removes the stigma of being singled out and ensures no pitcher gains an advantage simply because no one asked to inspect him. It’s the same principle behind drug testing in other sports. The checks are brief, lasting only a few seconds, and have become as routine as the national anthem.