MLB to crack down on foreign substances starting June 21

Major League Baseball will crack down on foreign-substance use beginning June 21, the league announced Tuesday.

Umpires will regularly check pitchers, even if the opposing club's manager doesn't make a request, to dissuade them from using illegal substances on the ball.

Starting pitchers will be subjected to more than one mandatory check per game, while relievers must be checked at the end of an inning, or after they're removed from a contest, MLB notes. To avoid delays, checks are expected to take place between innings or after pitching changes.

Any pitcher who possesses or has applied a foreign substance will be ejected from the game and automatically suspended, according to MLB. If a position player, such as a catcher, applies a substance to a ball to aid their pitcher, both players will be ejected and suspended.

Players who refuse to be inspected will also be ejected from the game and suspended.

Suspensions will last 10 games, and teams can't insert a roster replacement for players suspended for foreign-substance use, according to MLB.

Other club personnel are also subject to discipline for failure to comply with the league's new guidelines.

"After an extensive process of repeated warnings without effect, gathering information from current and former players and others across the sport, two months of comprehensive data collection, listening to our fans, and thoughtful deliberation, I have determined that new enforcement of foreign substances is needed to level the playing field," commissioner Rob Manfred said.

"I understand there's a history of foreign substances being used on the ball, but what we are seeing today is objectively far different, with much tackier substances being used more frequently than ever before," he added.

"It has become clear that the use of foreign substances has generally morphed from trying to get a better grip on the ball into something else - an unfair competitive advantage that is creating a lack of action and an uneven playing field," Manfred continued. "This is not about any individual player or club, or placing blame, it is about a collective shift that has changed the game and needs to be addressed. We have a responsibility to our fans and the generational talent competing on the field to eliminate these substances and improve the game."

Rosin bags will continue to be used on the mound, but the use of all other substances is against the rules and players will be punished. That includes mixing substances like sunscreen into the rosin.

The league has also advised pitchers not to apply sunscreen during night games or when playing in roofed stadiums.

MLB's guidelines come amid league-wide concern about pitchers using foreign substances to improve their performance.

A former Los Angeles Angels clubhouse manager named hurlers such as Gerrit Cole of the New York Yankees and Max Scherzer of the Washington Nationals as illegal-substance users.