Former Packers quarterback Brett Favre, who guided the franchise to a Super Bowl title in the 1996-97 season, posted a heartfelt tribute to Starr on Twitter.
"Bart Starr was the most kind, thoughtful and classiest person you could ever know," Favre wrote. "I consider myself extremely lucky to have called him friend and to have been mentioned in the same breath. Deanna and I are praying for Cherry and the Starr family."
Aaron Rodgers, another Packers quarterback who led the organization to a Super Bowl victory, posted a photo of Starr with a heart on Instagram, indicating his close friendship with the Hall of Famer.
Former Dallas Cowboys gunslinger Troy Aikman also took to social media to pay his respects. Aikman revealed that Starr visited him in the hospital after he had elbow surgery following the Cowboys' 1995-96 Super Bowl win.
Aikman said he wasn't sure how Starr even knew he was at the hospital.
"Bart Starr was a true gentleman and one of the kindest people I knew," Aikman wrote. "I had elbow surgery following our '95 Super Bowl in Birmingham and Bart made a visit to the hospital. To this day, not sure how he even knew I was there."
Starr, who played for the Packers from 1956-71, previously suffered two heart attacks and a serious stroke in 2014. He is the only quarterback in league history to win five championships in a decade.
Starr was named Most Valuable Player in Super Bowl I and Super Bowl II. He also earned the league's MVP Award in 1966 and was inducted into the Hall of Fame in 1977.
"While he may always be best known for his success as the Packers quarterback for 16 years, his true legacy will always be the most respectful manner in which he treated every person he met, his humble demeanor, and his generous spirit," Starr's family said in a statement.