One of America's most popular underdog basketball programs is getting a promotion.

ESPN.com's Andy Katz is reporting that Butler will leave the Horizon League, which has been a flagship member of conference since its 1979 inception, and head to the Atlantic 10 for the start of the 2013-14 season.

The official move is expected to come Wednesday, according to ESPN.com. The move completes a 14-team qouta within the league, since Temple is jettisoning for the Big East next year in basketball; the Owls' football program joins the Big East later this year, in the fall.

It's a win-win for Butler and A10, considering the school made back-to-back Final Fours -- an unprecedented accomplishment for a team not from a major conference -- and the conference has always been just one tier below other major, BCS leagues.

Under the sharp, lauded, straight-and-narrow Brad Stevens, Butler has a .777 winning percentage the past five seasons. As a program, Butler has made 11 NCAA tournaments and five Sweet 16s.

It is currently unknown whether or not the Atlantic 10 will stay at 14 teams with the Temple-Butler swap, or if two more schools -- currently rumored as VCU and George Mason from the CAA -- will climb aboard to create a 16-team league.