MLBTradeRumors.com published a story indicating that Burrell had hung up his spikes but did not cite a specific source. Fox Sports' baseball reporter Ken Rosenthal confirmed the news.
Burrell hit 18 home runs for the Giants in 2010. He batted .266 with 51 RBIs in 96 games that season, and took over as the everyday left fielder. But he spent much of 2011 battling a foot injury that limited him to 92 games.
Burrell was placed on the disabled list on July 15 with a mid-right foot strain and didn't play again until Aug. 31, though he was still in pain after missing 43 games.
On the last day of the season, a 6-3 loss to Colorado at AT&T Park, Burrell fought tears after running in from left field to a standing ovation before the start of the seventh inning -- Giants manager Bruce Bochy's way of honoring the veteran in what might have been his final game. An emotional Burrell hugged and high-fived his teammates and came back out of the dugout for a curtain call, waving to the fans.
He is No. 4 all-time on the Phillies' career home runs list. He won a World Series with Philadelphia in 2008.
The Associated Press contributed to this report.