The partnership between Major League Soccer and USL PRO, the third division in the pro pyramid, is a much-needed arrangement that promises to improve MLS’s long-term player development.

MLS’s inadequate reserve league prompted the move. For years, many young MLS players have languished without practical experience. They would train with the full squad but weren’t exposed to authentic competition. Often, reserve matches were postponed or guest players were summoned on short notice to fill out rosters. Games were usually played on weekday afternoons in front of small crowds.

“Over the past several years, USL PRO has made great strides in restructuring in a manner that serves to complement the objectives of MLS,” said Todd Durbin, an MLS executive vice president. “This is a win-win for all involved and it demonstrates our strong commitment to growing North American professional soccer at all levels.”

Under the new system, an MLS club participating in the program will send at least four players to a USL affiliate on a long-term loan. Those MLS teams will not compete in the reserve division. With only 13 USL sides, not all 19 MLS clubs will have a USL affiliate. But remaining reserve teams will play two games against a USL club, with the results counting in the reserve division and USL standings.

D.C. United is expected to partner with the Richmond Kickers and withdraw from the reserve league. Sporting Kansas City has already announced a deal with Orlando City.

Last year United sent homegrown midfielder-defender Conor Shanosky on a season-long loan to the second-division Fort Lauderdale Strikers in the NASL and arranged for second-year defender Ethan White (Richmond) and third-choice goalkeeper Andrew Dykstra (Charleston Battery) to play for USL sides.

This year, rookies and other inexperienced players would become top candidates for a USL assignment. They would remain eligible to play for the MLS squad.

USL franchises in 2013 are: Antigua Barracuda, Charleston Battery, Charlotte Eagles, Dayton Dutch Eagles Lions, Harrisburg City Islanders, Los Angeles Blues, Orlando City, Phoenix FC, Pittsburgh Riverhounds, Richmond Kickers, Rochester Rhinos, VSI Tampa Bay and Wilmington Hammerheads. (Phoenix and Tampa are expansion clubs.) In 2014, Sacramento will begin play.

“This new partnership with MLS will elevate and strengthen the level of competition for domestic professional soccer while simultaneously creating a more sustainable financial model for team owners,” USL chief executive Alec Papadakis said. “As a result, we expect this partnership will forge a seamless system for the development of players and coaches, and promote the expansion of professional soccer into new North American markets.”