The Yankees did announce on Tuesday that Sheppard would be unavailable at the commencement of the 2009 season, including the first exhibition games against the Cubs at the new Yankee Stadium this weekend and the April 16 home opener.
"I will not be able to be at Yankee Stadium for the series with the Cubs or Opening Day," Sheppard said in a statement released by the team. "My personal physician advised me to wait until I am ready. It is in the hands of God. I am looking forward to doing games in the new Stadium."
Sheppard -- nicknamed "The Voice of Yankee Stadium" and known for his clear, concise style -- did not appear at Yankee Stadium in person during the 2008 season due to a bronchial infection and his continuing recovery, though Derek Jeter used a recording of Sheppard for all of his home at-bats.
"I'll always come up to Bob Sheppard," Jeter said last year.
Sheppard taped a video message for the final Yankee Stadium game last Sept. 21, reading the lineups from his Baldwin, N.Y., home and providing a valedictory honoring the Yankees and their home since 1923.
"Farewell, old Yankee Stadium, farewell," Sheppard recited. "What a wonderful story you can tell. DiMaggio, Mantle, Gehrig and Ruth. A baseball Cathedral in truth."
While Sheppard remains as the Yankees official public-address announcer, Paul Olden will substitute for Sheppard on April 3, 4 and 16.
A 12-time Super Bowl public-address announcer, Olden's broadcasting career spanned 17 years, including two seasons in the Yankees' television broadcast booth alongside Bobby Murcer and Phil Rizzuto from 1995-96.
The Yankees have not said who would continue as the public-address announcer if Sheppard is unable to resume his duties past the home opener.
The 2009 season marks the 58th anniversary of Sheppard's debut as the Yankees' public-address announcer. His first game was on Opening Day, April 17, 1951, when the Yankees defeated the Boston Red Sox, 5-0.
To commemorate his service to the club, the Yankees have named the media dining room in the new Yankee Stadium "Sheppard's Place."