Manager Ryne Sandberg said the Phillies were playing with heavy hearts against the Marlins on Tuesday night.
"Our thoughts are with David, hoping for a quick recovery," Sandberg said. "I addressed the players about that. You could hear a pin drop in the room. Players came up to me afterwards with some questions about him."
Montgomery, along with co-owner Bill Giles, purchased the team in 1981 when he was also named executive vice president. Montgomery took over presidency in '97 when Giles stepped into his current chairman role.
"He's a guy that, in a lot of ways, is our biggest fan," Sandberg said. "In my experience with the Phillies, four years, he's a guy that sets the tone as far as being a family-oriented organization, first-class, doing things the right way and being the leader of the organization."
The Phillies' statement went on to say that Montgomery is expected to spend a week in the hospital and have some recuperation time at home before returning to work.
David Furones is an associate reporter for MLB.com.