Major League Baseball is making slight changes to its new pitch clock rules, according to a memo obtained by ESPN.

The changes will not alter the most significant portions of the mandates that have shaved 25 minutes off game times this spring.

The document -- the fifth of what a source called "clarification memos" sent by the league this spring -- was distributed Wednesday after players on the joint competition committee between the MLB Players Association and MLB requested various changes.

MLB, which has control over on-field rules, will continue with the parameters of the pitch clock that players have been using all spring: 15 seconds with the bases empty and 20 seconds with runners on base, plus the hitter needing to be "alert" in the batter's box with 8 seconds remaining.