The reigning Masters champion confirmed in a statement on X on Thursday that he won't participate in the league, which is scheduled to begin play in January and will hold weekly matches at SoFi Center in Palm Beach Gardens, Florida.
"I am sad to confirm that I will not be participating in the first TGL season," Rahm wrote on X. "While I still think it's a great opportunity, right now it would require a level of commitment that I can't offer. Best of luck to everyone [involved,] and may the best team win!"
In a statement to ESPN, TGL said it was working to replace Rahm on its 24-player roster.
"Jon is one of the most talented players in the game and we will miss him during the inaugural TGL season," TGL officials said in the statement. "We understand that players have to balance a lot of different facets of their professional and personal lives and respect Jon's choice and wish him well."
Sources told ESPN on Thursday that Rahm, who lives in Arizona, decided to back out of his commitment partly because of the travel required to get to South Florida.
"I'm thrilled to join Boston Common Golf and to be representing Boston and New England's rich sports culture," McIlroy said in a statement. "TGL brings a unique dimension to the game, and I can't wait to stand with Adam, Keegan, and Tyrrell as my teammates. It's a fantastic opportunity that will offer us all a chance to build lasting connections and to foster regional pride that you don't often see in the game of golf."
The Boston franchise is owned by Fenway Sports Group, which also owns the Boston Red Sox, Liverpool FC and the Pittsburgh Penguins.
"These four remarkable golfers have achieved an extraordinary list of accolades as individuals, and together as a group, they convey an unmistakable sense of exceptionalism that not only commands respect but also instills a profound sense of awe, especially among their competitors," Fenway Sports Group principal owner John Henry said in a statement. "Rory, Tyrrell, Keegan, and Adam stand at the very heart of our team's potential for success in this groundbreaking venture and we extend our gratitude to each of them for embarking on this journey with us."
On Tuesday, Atlanta Drive GC announced that two-time major championship winner Justin Thomas is its first player. Los Angeles Golf Club added two-time major championship winner Collin Morikawa on Wednesday.