Griffin, a two-time All-Star forward with the Los Angeles Clippers, has been diagnosed with a medial meniscus tear of his left knee and will not play in the London Games, Colangelo said.
"We are sorry to have received confirmation of Blake's injury which has forced his withdrawal from the USA Team for this summer," Colangelo said in a statement.
"Blake worked extremely hard in our training camp and certainly would have been a valuable contributor. This is another unfortunate injury, but we have to continue to move on and we're very fortunate to have Anthony Davis available.
"Anthony offers our team additional height and length, and this will be an incredible experience for him."
The 6-foot-11 (2.08 metre) Davis, who as a University of Kentucky freshman last season was the consensus college Player of the Year, was one of six alternates on the USA roster.
Davis, 19, was selected by the New Orleans Hornets with the number one overall pick in the June draft. He scored nine points against the Dominican Republic in the USA's 113-59 exhibition victory Thursday night.
Griffin, known for his rim-rattling dunks, averaged 20.7 points and 10.9 rebounds for the Clippers last season.
Griffin is the latest in a string of U.S. players hit by injuries ahead of the London Games, which begin in two weeks.
Orlando Magic center Dwight Howard, Chicago Bulls guard Derrick Rose, and Miami's center/forward Chris Bosh and guard Dwyane Wade have already been ruled out due to injuries. (Reporting By Steve Ginsburg in Washington; Editing by Julian Linden)