As a result of alleged cheating, the MLB is cracking down even harder on sticky stuff.

Pitchers began cheating again late last season after learning workarounds to the routine checks by umpires, according to a letter released by Major League Baseball to its clubs on Friday. The brief is a tacit admission that the league will continue to tighten down on sticky substances. Starting this weekend in spring training games and continuing throughout the season, umpires will inspect the top and bottom of a pitcher's hand when performing random between-innings inspections of the pitcher. Pitchers' hats, belts, and gloves can still be examined by umpires, as they were allowed to do last season beginning in June.

"If an umpire's inspection reveals that the pitcher's hand is unquestionably sticky or shows unmistakable signs of the presence of a foreign substance, the umpire will conclude that the pitcher was applying a foreign substance to the baseball with the intent of gaining an unfair competitive advantage," wrote Mike Hill, senior vice president of baseball operations, in a memo to clubs obtained by Sports Illustrated. In such a circumstance, the pitcher is expelled and his or her career is automatically suspended.

"If an umpire watches a pitcher attempt to wipe off his hands prior to an inspection, he may be susceptible to immediate dismissal," Hill wrote in the memo.

Catchers and position players, both of whom have the potential to harbor spies, are subject to the same restrictions. According to the memo, starting pitchers "should expect more than one obligatory check every game" in the future. Each relief pitcher will be checked at least once throughout his or her shift. The Major League Baseball is reacting to data that implies that pitchers have learned to get around the checks. They would be able to play tic tac toe avoid detection if they did not keep a supply of sticky stuff stashed on their hat, belt, or gloves. The new MLB standards assume that no matter what method is used, a pitcher who utilizes a sticky material will eventually get it on his or her hands or fingers, which is why the league has added an additional degree of examination.

According to the most recent monthly statistics available, the spin rates on four-seam fastballs and sliders dropped precipitously as the crackdown began in June, but then began to rise again late in the season:

Another method of determining how well pitchers performed in the face of inspections is to look at the relationship between velocity and spin rate. In the previous season, MLB began the crackdown with inspections on June 21, but did not notify pitchers of the change until June 3. It plummeted almost immediately, but the ratio of fastball spin to velocity started creeping back up late in the season:

When the crackdown started, it was in response to rising spin rates and declining batting averages. Pitchers have been experimenting with various things, such as mixing sunscreen with rosin, to improve their grip on the baseball for years. In order to remove the sheen from new baseballs, they are wiped with mud long before a game begins. By game time, however, the mud has dried and can leave a slick residue.

Pitching pitchers began to use considerably stickier substances not only for grip but also as a performance enhancer when spin rate and spin axis devices became more widespread, specifically in order to achieve higher pitch quality metrics than they were otherwise capable of. A common chemical in strongman contests is Spider Tack, which participants use to lift Atlas stones weighing approximately 100 pounds, which is one of the most popular compounds. In an interview with SI's Stephanie Apstein and Alex Prewitt for their investigation into sticky stuff from last June, a recently retired pitcher stated that 80 percent to 90 percent of pitchers were using some type of banned chemicals prior to the initial crackdown.

Every year from 2017 to the first two months of the previous season, the average four-seam spin rate grew by a small amount. Following the initiation of the crackdown, the four-seam spin rate fell to its lowest level since 2015. (2,252 rpm).