Major League Baseball sent a memo to farm directors Tuesday indicating that beginning on June 25, all Triple-A games will use the automated ball-strike (ABS) challenge system as opposed to full ABS, which was previously used for half the week.

The move is another indication that the league is inching toward implementing the challenge system at the major league level, though commissioner Rob Manfred has said that move is still at least another season away from happening.

The memo, obtained by ESPN, says the league's research indicates that both in-uniform personnel (players and coaches) and fans prefer a challenge system over full ABS.

In the challenge system, challenges to calls on balls and strikes are made by the hitter or catcher in real time with the umpire receiving an answer to the challenge via an earpiece. In full ABS, every call is made for the umpire.

For the first half of this season at Triple-A, full ABS was used for Tuesday-Thursday games while the challenge system was used for weekend contests. Now, all games will have the challenge system.

Additionally, the International League will experiment with teams only receiving two challenges per game instead of three, which has been the norm. That change is being implemented in an effort to reduce the frequency of high-challenge games. The league memo indicates that 89% of fans believe the optimal number of challenges per game is six or fewer; however, almost 40% of Triple-A games featured more than six. In all cases, teams retain the challenge if they are successful.

Interestingly, in surveys with fans and players, the league found that not only do they prefer the challenge system over full ABS, they also prefer the current system -- umpires making all calls -- over full ABS:

• 61% of team personnel, including players, and 47% of fans prefer the challenge system.

• 28% of personnel and 30% of fans prefer human umpires making all calls.

• Only 11% of personnel and 23% of fans want full ABS.

According to sources familiar with the experimentation in the minor leagues, the earliest any system could be implemented at the major league level is 2026.