The Tampa Bay Rowdies and Ottawa Fury will leave the second-tier North American Soccer League to join the third-division United Soccer League next season, the clubs and the USL announced on Tuesday.
The long-rumored moves come during a time of turmoil for NASL, which will also lose Minnesota United to top-flight MLS in 2017.
"We are excited to join the United Soccer League," Rowdies chairman and CEO Bill Edwards said in a press release. "I have said from the day I acquired controlling interest in this club that I wanted to make it one of the most successful teams in North America.
"The Rowdies' move to the USL is a positive step toward reaching the long-term goals of the club."
The original Tampa Bay Rowdies were founded in 1975. They competed in the old NASL before that circuit, then the top league in the U.S., folded in 1984. They continued to operate in other leagues until 1993 before being revived in 2008 as FC Tampa Bay.
Edwards renamed them the Rowdies in 2011 after acquiring rights to the iconic name, and they went on to claim the NASL title a year later.
The Fury debuted in the NASL two years ago. They replaced an amateur club of the same name, which played in the USL's Professional Development League, or fourth tier, between 2005 and 2013.
"The USL is a strong professional league that's getting stronger," said Fury coach and general manager Paul Dalglish, who previously managed the USL's Austin Aztex. "I know our fans will be impressed."
Ottawa advanced to their only Soccer Bowl last season, losing to the New York Cosmos.
The departure of Ottawa and Tampa Bay leaves NASL with 10 clubs. That includes the expansion San Francisco Deltas, who will join the league next season, but also the financially troubled Fort Lauderdale Strikers and Rayo OKC. The future of both of those clubs remains uncertain.
"The NASL operates in an environment where owners are free to take their clubs wherever they choose," league commissioner Bill Peterson said Tuesday in a statement.
"All we can do is acknowledge that reality and move forward with our business, which is exactly what we're doing right now. We've never had a stronger and more unified group of owners who are committed to the league's model, its structure, and its long-term vision."
Peterson went on to say that the NASL remains committed to growth despite the defections, "with a half-dozen serious expansion discussions in progress."
The Rowdies and Fury played to a 1-1 draw Saturday in their final NASL meeting. Both clubs will play their last games in the league this weekend, with Tampa visiting the Jacksonville Armada and Ottawa hosting the Strikers.
The USL concluded its season on Sunday, with the New York Red Bulls II defeating Sporting Kansas City affiliate Swope Park Rangers in the championship match.