initiatives and rules intended to develop young players. Rules concerning Generation Adidas players and home grown players provide incentives for clubs to develop and retain young players. MLS has required all of its teams to operate youth development programs since 2008. MLS roster rules allow teams to sign an unlimited number of players straight from their academies and bypassing the draft process. There is also supplementary salary budget made by MLS only for homegrown players that are registered using senior roster slots called homegrown player funds. One of the most prominent and lucrative examples of success in "home-grown" development was Jozy Altidore, who rose to prominence as a teenager in MLS before his record transfer fee $10 million move to Villarreal in Spain in 2008. The various MLS teams' development academies play matches in a U.S. Soccer developmental league against youth academies from other leagues such as the North American Soccer League (NASL), which had been a Division II league prior to 2018, and USL Pro, originally a Division III league but now the Division II USL Championship. The league operates a Generation Adidas program, which is a joint venture between MLS and U.S. Soccer that encourages young American players to enter MLS. The Generation Adidas program has been in place since 1997, and has introduced players such as Landon Donovan, Clint Dempsey, Tim Howard and Michael Bradley into MLS. Players under the Home Grown Player rule are signed to Generation Adidas contracts, all players on Generation Adidas contracts are "off budget players" and their salaries do not count against the cap. MLS has operated reserve leagues, which give playing time to players who were not starters for their MLS teams, during two different periods. The MLS Reserve League was formed in 2005, and operated through 2014 (with the exception of the 2009 & 2010 seasons). MLS began integrating its Reserve League with the league then known as USL Pro in 2013, and after the 2014 season folded the Reserve League, with MLS then requiring all teams to either affiliate with a USL team or field their own reserve side in that league. However, this requirement was never strictly enforced, and MLS eventually relaunched its reserve league in 2022 under the banner of MLS Next Pro. In the inaugural 2022 season, 19 of the league's then-current clubs, plus future club St. Louis City SC, fielded reserve sides in Next Pro.