Major League Baseball's emphasis on stopping pitchers from using foreign substances is set to begin Monday.

Less than a week after MLB provided all clubs with a memo laying out the new guidelines, umpires will be empowered to inspect hurlers after each appearance, per ESPN's Jesse Rogers. Closers will be inspected for substances on their person prior to entering the game. 

Pitchers can also be inspected between innings and after they come out of a game—or between at-bats—but not during an at-bat, unless the umpire has reason to suspect the pitcher of doctoring the ball.

Pitchers found using foreign substances will be ejected and subject to a 10-game suspension. 

As part of the June 15 memo, MLB Commissioner Rob Manfred made clear the practice of applying grip enhancers is no longer tolerable:

“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. 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.”

Rogers noted June has seen the lowest strikeout and walk rates while producing the highest batting average and on-base percentage of any month this season. 

Players across the sport have sounded off on the memo. 

Tampa Bay Rays star Tyler Glasnow recently said the lack of substances contributed to his partial UCL tear and flexor strain.

Batters like New York Mets slugger Pete Alonso have also criticized MLB, arguing—without providing evidence—the league "manipulates the baseballs year in and year out depending on the free-agency class." Alonso went on to say giving pitchers a better grip on the ball can also keep batters safer, as better control results in fewer players getting hit by a pitch.

With changes looming Monday, players across the game will find themselves in a midseason experiment intended to increase action in baseball.