Major League Baseball informed teams and players Thursday afternoon that its efforts to crack down on pitchers' use of illegal substances will be enhanced in 2023, according to industry sources briefed on the contents of a league memo.

The enhanced examinations, approved by the league's on-field committee, will entail more detailed inspections by umpires and inspections that occur more often than they have over the past 21 months.

"Umpires have been instructed to increase the frequency and scope of foreign substance checks this year, including randomized checks of fingers (including removal of rings worn on either hand of pitchers), hands, hats, gloves, belts/waistlines, and pants," the memo states. "Pitchers may be subject to checks before or after innings in which they pitch, and managers may make inspection requests of a pitcher or position player either before or after an at-bat."

According to the memo, umpires can focus on "suspicious behavior by players that suggests the potential use of foreign substances."

"For example, if an umpire observes a pitcher attempting to wipe off his hands prior to an inspection the player may be subject to immediate ejection for violating the rules by attempting to conceal a foreign substance," the memo states. "In addition, catchers will be subject to routine inspections, including checks on their equipment."

There was concern among team officials late last season that some pitchers had started to ignore the enforcement of the illegal substance rules, which were ratcheted up during the 2021 season. Over the past two seasons, umpires have met pitchers as they came off the mound to check their hands, hat or belt for substances, a predictable routine.

During the 2022 season -- particularly in the second half -- the spin rates of some pitchers began to rise. To some team officials, this was clear sign that the use of Spider Tack or other substances that help pitchers grip the ball was on the rise again.

In meetings with umpires earlier this offseason, MLB instructed them to be more thorough and less predictable in their checks of pitchers and showed video of what were deemed effective checks and what checks were viewed as less effective.

For example: Before the 2021 crackdown, many pitchers could be seen using their pitching hand to rub the wrist area of their gloved hand. The assumption of some managers and coaches has been that this may have been a means of applying an illegal substance. That practice could be seen more commonly in the later stages of the 2022 season.

According to sources, the umpires were told that they didn't have to wait for a manager to ask for a check of an opposing pitcher; rather, MLB wants the umpires to call for a check if they see something suspicious.

The memo was issued by Mike Hill, MLB's senior vice president of on-field operations, and sent to team executives, managers and players in the major and minor leagues.

Hill reiterated that teams and club officials found to have fostered the use of illegal substances will face discipline.

According to the memo, "Clubs will be held accountable for any foreign substances discovered in any Club area (e.g., clubhouse, tunnel, dugout, bullpen, etc.). ... Clubs and Club personnel also may be subject to discipline by the Commissioner for failing to adequately educate and manage or police their staff and players to ensure compliance with the rules."