• The Philadelphia Union became the 16th MLS team in 2009.soccer ball image by Rich Johnson from Fotolia.com
  
  Major League Soccer is one of the fastest-growing professional sports leagues in North America. The Philadelphia Union became the 16th team to join MLS prior to the start of the 2010 season, and it held an expansion draft to form its opening-day team. Players used to construct the Union roster were selected from a pool provided by the league's other 15 teams.
  
  

Eligible Players

• Prior to the expansion, all teams were given a window in which they were permitted to make trades in order to finalize their rosters. Once they determined the players they wanted to keep, and which ones would be made available for drafting, their final lists were submitted to the MLS head office. Each team was allowed to protect 11 players between their senior roster (the main team) and their development roster (the second-tier or minor-league team). Even if a player's contract was set to expire at the end of 2009, he was still considered part of the team for which he last played.
  
  

International Players

• The number of international players the 15 existing MLS teams could make available at the expansion draft was also restricted. An international player is defined as any non-domestic player competing in the U.S. This rule varied slightly for Toronto FC, the only Canadian entry in the league. Although U.S. players competing for a Canadian team would normally be considered "non-domestic," MLS ruled that both American and Canadian players suiting up for Toronto FC were exempt from being considered international players. Each team was allowed to expose a number of international players equal to three less than the total number on their roster.
  
  

Draft Selections

• Once the Union was given finalized lists of the nearly 200 available players, the franchise began building its initial roster on Nov. 25, 2009. The draft lasted a total of 10 rounds. Each team was only eligible to lose a maximum of one player. After a team lost a player to the Union, its remaining available players were taken out of play. Five teams didn't have any players selected: Dallas, Houston, Kansas, Salt Lake City and Toronto.