The Major League Baseball Players Association took an initial step toward unionizing the minor leagues Sunday night, sending out authorization cards that will allow minor league players to vote for an election that could make them MLBPA members, union executive director Tony Clark told ESPN on Sunday night.

The potential unionization of more than 5,000 minor leaguers is the latest action in a yearslong effort by players who won a $185 million settlement from the league in an unpaid wages class-action lawsuit and have received housing from teams and increased pay in recent years. Minor league players, whose compensation and benefits are not collectively bargained, continue to argue for higher salaries, which for a vast majority range from around $5,000 to $14,000 annually. Furthermore, the Senate Judiciary Committee has suggested it will call a hearing to explore MLB's antitrust exemption and its treatment of minor leaguers.

Advocates for Minor Leaguers, the group that has spent recent years organizing minor league players, is now working with the MLBPA, which collectively bargains with MLB on behalf of the 1,200 players on major league rosters.

"The last couple years has been a buildup of players offering their voices and their concerns, with Advocates for Minor Leaguers continuing to echo and aggregate those voices in a way that have gotten us to this point," Clark told ESPN.

In order for the MLBPA to represent minor leaguers in collective bargaining, 30% of players need to sign union authorization cards, which would prompt an election. If a majority of those who vote in an election choose for union representation, the National Labor Relations Board will require MLB to recognize the union. The league and MLBPA then would collectively bargain for minor leaguers, an outcome that even five years ago would've registered as farfetched.