The move is retroactive to Saturday. A corresponding roster move will be made before Tuesday night's game with the Milwaukee Brewers.
LaRoche is batting .172 in 43 games, after being signed to a two-year contract worth $16 million to succeed Adam Dunn at first base.
"Adam is basically saying, 'It doesn't hurt, but I can't believe I'm missing these pitches,'" manager Jim Riggleman said. "'So, maybe it's something there that's not allowing me to get to the ball.'
"We've got to explore that. No throwing activities, no lifting, no swinging."
LaRoche was examined in New York on Monday, and will be given time to rest his ailing shoulder, Riggleman said. If the rest does not heal his shoulder, surgery could be an option, according to the manager.
"I don't know if the answer is more rest or something more drastic," Riggleman said.
Michael Morse was slated to make his fourth start at first base in Monday night's game against the Brewers, but Riggleman said he would make decisions on who would replace LaRoche on a daily basis. Both Alex Cora and Matt Stairs could also play first.
Center fielder Rick Ankiel was slated to play in a rehab game for Double-A Harrisburg on Monday night, and could be summoned to take LaRoche's spot on the roster. Riggleman said Ankiel could be an option to play first base on occasion and would take some infield practice.
Bill Ladson is a reporter for MLB.com. Joe DiGiovanni is a contributor to MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.