LaRoche has been on the disabled list since May 22, hoping to recover without surgery and return to the team, but his shoulder had not improved. Washington general manager Mike Rizzo said he met with LaRoche and team doctors Tuesday and decided to schedule the operation.
"In my gut a couple weeks ago, I thought there was a chance this would happen," LaRoche said. "I'm confident we've done everything we could possibly do to find out if it needs surgery or not. I'm comfortable with it now."
Dr. Wiemi Douoguih, the Nationals' medical director, will perform the procedure.
Douoguih said the extent of the injury will not be known until the surgery. LaRoche's recovery could take anywhere from three to seven months, depending on the severity of the tear, Douoguih said. LaRoche said he was aiming for a 5-to-6 month process.
"If all goes right, he'll be 100 percent by the beginning of spring training next year," Rizzo said.
LaRoche was hitting .172 with three home runs and 15 RBI in his first season with the Nationals. He batted .261 with 25 home runs and a career-best 100 RBI last year for Arizona.
Seeking some much-needed pop in the middle of the lineup, Washington signed LaRoche to a $16 million, two-year contract last offseason.
LaRoche said he had felt pain when throwing during spring training, but he tried to play through it as long as he could swing.
"The MRI in spring training had a small tear, the recent MRI had a very large tear," LaRoche said. "That's got to make you believe that going out and playing, it just got worse and worse. It finally got to the point where we are now, got to go in and clean it up."
LaRoche said he has never before undergone any surgical procedure.
"I've been really lucky for the last 10, 11 years, however long I've been in pro ball, to not have a ton of injuries," LaRoche said. "This is pretty new to me."