"Pat Gillick will be in his stead on an interim basis," Amaro said. "I'm the GM. That's not going to change. Ryno's the manager. That's not going to change. And we'll go about our business status quo."
The organizational fallout from Montgomery's health problems - he underwent surgery in May to remove cancer from his jawbone - remains unknown. Amaro preached normalcy but withheld details, given the situation's sensitivity. Gillick, the team's former general manager, was not made available for comment and did not return phone calls.
The 77-year-old executive became a Hall of Famer because of his accomplishments in baseball operations. Now, he must oversee the franchise's business matters, too.
In recent years, Gillick expressed interest in vacant team president posts with the Seattle Mariners and Chicago Cubs. Those discussions never reached formal stages.
Left unclear is whether Gillick has the same autonomy Montgomery, one of the game's most respected executives, enjoyed. He had complete management authority from the silent ownership group. Three families - the Bucks, Betzes and Middletons - are longtime partners.
Until Thursday, Gillick worked for Amaro as an adviser. He became Amaro's boss in Montgomery's absence, but Amaro insisted baseball decisions will be made in the same manner as before.
"There's no change," Amaro said. "There's no change."
Many of the baseball operations employees have ties - some of them in the form of longtime friendships - to Gillick. He wielded strong influence in the hiring of Amaro over Mike Arbuckle to succeed him as general manager after the 2008 season. Gillick could be authorized to make whatever changes he deems beneficial; the termination of Amaro may not be one.
Amaro is under contract as general manager through 2015. He has relied on Gillick's input on roster moves since replacing him.
Gillick is best known for his success in Toronto and Seattle, although one of his greatest accomplishments might have been persuading Montgomery and Phillies ownership to think bigger in the mid-2000s. Gillick came to Philadelphia as an outsider and was able to penetrate a fiercely loyal organization.
Now, his loyalty to Amaro will be tested.
The team said Thursday that Montgomery would return to run the team "when he is fully recovered." Amaro would not speculate on a timetable.
"Whenever David's back and physically able to come back, he will be back, and he will take his role," Amaro said.
When asked about Montgomery, manager Ryne Sandberg said, "I was advised to keep it at a minimum." He stressed what was on the minds of many team employees who cherish the familial management style Montgomery embodied.
"Prayers and thoughts are with him for a speedy recovery," Sandberg said.
Montgomery was believed to have concluded chemotherapy and radiation treatments. He maintained a regular schedule at Citizens Bank Park even as his health declined. The decision to step aside was not rushed; a team source said the possibility was discussed in recent meetings.
"We're all concerned about David, and that's really the priority." Amaro said. "We're not really at liberty to really discuss much more about it."