Gillick, who served as the organization's general manager from 2005-08 and continued to work as a senior advisor, issued a statement that said, "I have the highest regard for David Montgomery, as does everyone in our industry. I am glad to be of assistance to the Phillies."
The team added in its statement: "The club looks forward to David returning to his roles as General Partner, President and Chief Executive Officer when he is fully recovered."
Montgomery, 68, had surgery May 19 to remove cancer from his right jaw bone. He had been undergoing treatment following the surgery. Montgomery has kept a low profile since, although he was first in line Wednesday to shake hands on the field with the Taney Little League team during a pregame ceremony at Citizens Bank Park.
Montgomery had been unavailable to reporters in recent weeks, although he spoke to a fan group last week at the ballpark. He also recently made the team's road trip to Washington before the July 31 non-waiver Trade Deadline.
Montgomery has been the public face of the Phils' ownership group since 1997, when he became president. He started in the organization in 1971, when he sold season and group tickets. Montgomery advanced to marketing director and director of sales, before becoming executive vice president following the 1981 season.
Montgomery became chief operating officer in 1992. He acquired an ownership interest in the team in 1994.
Montgomery is very popular with his employees. Former players often cite the organization's "family atmosphere," and it is something that starts with Montgomery, who makes a point to know everybody in the organization, regardless of their stature or importance.
Montgomery grew up in the Roxborough section of Philadelphia. He graduated from William Penn Charter School in 1964 and the University of Pennsylvania in '68. Montgomery received his MBA from the Wharton School in '70.
Montgomery and his wife Lyn have three children: Harry, Sam and Susa. They have two grandchildren: Elizabeth and Cameron.
Todd Zolecki is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.