Beginning Monday, Major League Baseball will enhance its enforcement of the rules that prohibit applying foreign substances to baseballs.

MLB announced Tuesday that it has provided guidance to all 30 clubs and to the umpires to serve as “a uniform standard for the consistent application of the rules, including regular checks of all pitchers regardless of whether an opposing club’s manager makes a request.”

Under the new guidelines, any pitcher who possesses or applies foreign substances in violation of the rules will be ejected from the game and automatically suspended in accordance with the rules and past precedent. Suspensions under Rule 3.01 are 10 games. Starting pitchers will have more than one mandatory check per game, and relievers must be checked at the end of the inning when they entered the game or when they are taken out of the game, whichever comes first. Typically, the inspections will take place between innings or during pitching changes to give the umpires ample time to perform a thorough check without delaying the game.

Players will be paid during suspensions for this violation; repeat offenders will be subject to progressive discipline. Clubs and club personnel will also be subject to discipline for failure to ensure compliance with these rules.

“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 in a statement. “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. It has become clear that the use of foreign substance 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.”

Though Rules 3.01 and 6.02(c) and (d) prohibit applying foreign substances, use of sticky substances has been widespread and tacitly accepted by managers, players and teams for decades as a means of reducing the slickness of the ball and improving control of pitches.

But as pitchers have learned how to use substances to improve their spin rates, the issue and its effect on offensive performance has become much more pronounced, leading to this league intervention.

MLB had informed clubs prior to the 2021 season that it would make an effort to quantify the prevalence and effects of foreign substances in the sport through the use of data collection, on-site monitoring of the clubhouse and dugout areas, video review and the collection of balls taken out of play. This process, along with complaints from position players, pitchers, umpires, coaches and executives, spurred the new guidelines.

“This is not about any individual player or club, or placing blame,” said Manfred, “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.”

Bill Miller, president of the Major League Umpires Association, issued a statement in support of MLB’s decision.

“The integrity of the competition is of utmost importance to us,” Miller said. “We have worked diligently with MLB to develop an enforcement system that will treat all players and clubs equally.”

Rule 3.01 states that “no player shall intentionally discolor or damage the ball by rubbing it with soil, rosin, paraffin, licorice, sandpaper, emery paper or other foreign substance.” Rule 6.02(c) expands on that rule by stating, among other things, that a pitcher may not “apply a foreign substance of any kind to the ball;” “deface the ball in any manner;” throw a shine ball, spit ball, mud ball or emery ball; “have on his person, or in his possession, any foreign substance;” or “attach anything to his hand, any finger or either wrist (e.g., Band-Aid, tape, Super Glue, bracelet, etc.).”

One argument offered by some pitchers in favor of the use of foreign substances is that it will prevent injury by limiting the number of batters hit by pitches. However, the number of hit batsmen is higher than it has ever been, with the four highest HBP rates since 1901 all coming in the past four years, suggesting that the foreign substances used by pitchers are doing little to protect hitters.

Details of the enhanced enforcement protocols are as follows:

• Starting pitchers will have more than one mandatory check per game, and each relief pitcher must be checked either at the conclusion of the inning in which he entered the game or when he is removed from the game (whichever occurs first). In general, inspections will be conducted between innings or after pitching changes to avoid a delay of the game and to allow the umpire to perform a thorough check, including the hat, glove and fingertips of the pitcher.

• Umpires may perform a check at any time during the game when the umpire notices the baseball has an unusually sticky feel to it, or when the umpire observes a pitcher going to his glove, hat, belt or any other part of his uniform or body to retrieve or apply what may be a foreign substance.

• A player who possesses or applies foreign substances in violation of the playing rules will be immediately ejected from the game and suspended. The umpiring crew shall be the sole judge as to whether the rules have been violated.

• The use of foreign substances is not subject to challenge using the replay review system.

• Although the foreign substance prohibitions do not apply exclusively to pitchers, the pitcher ultimately will be responsible for any ball that is delivered with a foreign substance on it. If a player other than the pitcher is found to have applied a foreign substance to the baseball (e.g., the catcher applies a foreign substance to the baseball before throwing it back to the pitcher), both the position player and pitcher will be ejected and automatically suspended.

• Catchers will also be subject to routine inspections. Umpires will also inspect a position player if they observe conduct consistent with the use of a foreign substance by the pitcher. Position players will not be ejected for having a foreign substance on their glove or uniform unless the umpire determines that the player was applying the substance to the ball in order to aid the pitcher.

• A player who refuses to cooperate with an inspection conducted by the umpire will be presumed to have violated the rules, resulting in an ejection from the game and a suspension.

• Rosin bags on the mound may be used in accordance with the rules. All substances except for rosin are prohibited per the playing rules that clearly state players cannot “apply a foreign substance of any kind to the ball” and may not “have on his person, or in his possession, any foreign substance.” Players may not intentionally combine rosin with other substances (e.g., sunscreen) to create additional tackiness or they risk ejection and suspension. Pitchers have been advised not to apply sunscreen during night games after the sun has gone down or when playing in stadiums with closed roofs. To ensure standardization of the rosin bag, clubs must submit the rosin bag along with the game balls to be reviewed by the umpires before the start of each game.

• Club personnel who help players to use foreign substances, handle foreign substances, mask player use of foreign substances, interfere with collections of baseballs or otherwise fail to report such violations of the playing rules will be subject to fines and/or suspension by the Commissioner.

• Any club employee who encourages a player to use foreign substances, or otherwise trains a player how to utilize a foreign substance in violation of the rules, will be subject to severe discipline by the Commissioner up to and including placement on the ineligible list.

• Clubs and club personnel are subject to sanctions for failing to adequately educate and manage or police their staff and players to ensure compliance with the rules. The Department of Investigations will investigate clubs whose players repeatedly violate the rules to determine the extent to which club personnel were aware of or otherwise condoned the practice.

• Clubs may not replace on the roster a player who is suspended for any on-field violation.

• MLB will closely monitor the effect of this policy on competition, and on player health, and may make future modifications to the enhanced enforcement guidance as appropriate.