Minor league baseball players and Major League Baseball struck a tentative deal Wednesday on the first collective bargaining agreement between the sides that will more than double player pay and represents the largest-ever gains in the rights of minor leaguers, sources familiar with the agreement told ESPN.

The deal, which will last for five years, comes after a rapid and successful effort last year by minor leaguers to unionize under the umbrella of the Major League Baseball Players Association and follows previous improvements in housing and pay. MLB formally recognized the union upon its formation, paving the way for a negotiation that finalized the deal on the eve of major league Opening Day.

After years of disillusionment among future major leaguers about paltry salaries forcing them to work offseason jobs — and coincidentally on the day a judge approved a $185 million settlement the league will pay players who accused it of violating minimum-wage laws — the parties agreed on a deal that went out to a vote among the union’s rank and file and that will need to be approved by owners, as well, before it is formalized. The agreement could be announced officially as early as Friday, the first day of games in the minor leagues.

The pay increases at each level are significant, according to sources, and will pay players for most of the offseason as well as spring training, including back pay for this season. At each level, the pay structure will see annual minimum salaries go from:

• Triple-A: $17,500 to $35,800

• Double-A: $13,800 to $30,250

• High-A: $11,000 to $27,300

• Single-A: $11,000 to $26,200

• Complex league: $4,800 to $19,800

Among those not included in the deal are players at teams’ complexes in the Dominican Republic. The minor league unit of the MLBPA includes only players on teams’ domestic rosters — and players from the Dominican Republic, Venezuela and other foreign countries will still reap the benefits when stateside.

The deal includes the reduction of the maximum Domestic Reserve List, which governs the number of players a team can roster outside of its Dominican Republic complexes, from 180 to 165 starting in 2024. The union had previously fought MLB’s efforts during the lockout last year to reduce the reserve list, which teams had identified as a priority.

Players, meanwhile, emphasized better housing and transportation as a matter of import. Starting in 2024, those at Triple-A and Double-A will receive their own bedroom, and players with spouses and children will receive special accommodations. In rookie ball, Single-A and High-A, teams will provide transportation to stadiums, where they’ll eat meals provided under rules negotiated by a joint clubhouse nutrition committee.

The overhaul of the minor leagues started in earnest via social media posts from players, who showed minuscule paychecks and often packed a half-dozen players into a one- or two-bedroom apartment, sleeping on air mattresses. While players started to organize, MLB was completing a takeover of Minor League Baseball. In doing so, it reduced the number of affiliated teams from 162 to 120. Under the terms of the agreement, MLB cannot contract teams over the next five years, though it already was unlikely to do so, with the Professional Development League licenses all minor league franchises signed before the 2021 season lasting 10 years.

Since MLB took over management of the minors, it had slightly increased pay in 2021 and offered housing in 2022. The league’s recognition of its substandard player compensation package forced it in a better direction, but players continued to push for more, and the leaps forward in the agreement between the parties codify a wide array of policies not previously part of minor league life, including:

• Pay from Jan. 2 until the Friday before Thanksgiving. From the next day through Jan. 1, players will not receive pay. There will also be slight annual pay increases in 2025, 2026 and 2027.

• A six-year reserve, instead of seven years, for future players who enter affiliated baseball at 19 or older. The shorter reserve period allows players — most of whom will have played in college — to reach minor league free agency earlier.

• Full name, image and likeness rights, which previously had been controlled by the league. By receiving them, the union can leverage group-licensing deals.

• Expanded medical rights, including, under some circumstances, the right to a second opinion on an injury as well as an expanded time period for post-injury medical expenses to be covered.

• Joint drug and domestic violence policies, to be patterned after the agreed-upon policies previously negotiated by the league and union.

• A no-strike, no-lockout provision under the terms of the deal, which will run until after the 2027 season.

In addition to the class-action case, pressure from Capitol Hill narrowed the focus on MLB and certainly hastened the changes. Advocates for Minor Leaguers, a group started by former minor league pitcher Harry Marino, had pushed Congress to force MLB to offer the same protections for minor league players as major leaguers. The Senate Judiciary Committee pressed MLB in a June 2022 letter about its antitrust exemption, and less than a month later, the league settled the antitrust suit, which also had been litigated by another former minor league pitcher, Garrett Broshuis, who had been at the forefront of early organizing.

By mid-September, minor leaguers voted to form a unit as part of the MLBPA, which Marino joined. He and Bruce Meyer, who was the lead negotiator on the major league CBA that was finalized in March 2022, were joined by union general counsel Ian Penny and MLBPA executive director Tony Clark in negotiations with MLB deputy commissioner Dan Halem and Colorado Rockies owner Dick Monfort, among others with the league.

The deal stabilizes baseball’s entire affiliated landscape for at least the next four years as the sport enters a vital period during which it will introduce a suite of new rules, including a pitch clock. Across the sport, minor leaguers who more than doubled their salaries overnight expressed appreciation, and Broshuis celebrated what many saw as a landmark win with a series of tweets that ended:

“For those who passed a hat around for diaper money for newborns.

“For those who grinded away at 2 or even 3 off-season jobs.

“For those who skipped breakfast or even lunch to pinch pennies.

“For those who have [given] up the game not for a lack of talent but for a lack of funds.

“This is for you.”