Major League Baseball is making slight changes to its new pitch clock rules but will not alter the most significant portions of the mandates that have shaved 25 minutes off game times this spring, according to a memo obtained by ESPN.

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 earlier in the week.

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.

"On one hand, we are prepared to make adjustments based on input," commissioner Rob Manfred said Tuesday. "On the other hand, we want to give it a chance to see how it plays out exactly over a period of adjustment in some regular-season games before we make any significant alterations."