Griffey was held out of Thursday's game in St. Louis because of soreness in his chest. A chest X-ray on Friday revealed the problem, which is not expected to be long-lasting. He pinch-hit in the seventh inning against Pittsburgh, drawing a walk before being replaced by a pinch-runner.
Griffey recently sat out four games because of diverticulitis, a colon condition that was initially diagnosed six months ago.
Players' union head Donald Fehr doesn't plan to be at the ballpark if and when Barry Bonds sets the career home run record.
"I won't follow him around, but I generally don't go to games during the season, so that's nothing new for me," Fehr said during a meeting with the Associated Press Sports Editors.
"My guess is it's probably possible if not likely that somebody from our office will be there because Bobby Bonilla is in the office and he'll probably go," Fehr said.
Boston Red Sox pitcher Curt Schilling offered $1 million to anyone who could prove it was not blood that blotted his famous sock in the 2004 playoffs, and criticized members of the media in a blog on his website.
Baltimore Orioles broadcaster Gary Thorne had said Red Sox catcher Doug Mirabelli had told him it was paint, not blood, and that it was done for a publicity stunt. Mirabelli called that a lie, and Thorne said Thursday he had misreported what Mirabelli said.
Seattle Mariners left-handed reliever Arthur Rhodes will miss the entire season after deciding to have surgery on a torn ligament in his pitching elbow.
Rhodes, 37, will have Tommy John surgery Wednesday in California.