Barry Bonds' new one-year deal with the San Francisco Giants is in doubt after a last-minute hitch with the contract.
Bonds joined the San Francisco Giants in 1993
Newspaper reports in New York said Major League Baseball commissioner Bud Selig had rejected the deal over a personal appearance clause.
Bonds'agent Jeff Borris told the New York Daily News: "At this time, Barry is not signing the new documents."
The initial signing followed two months of protracted talks and wss reportedly worth in the region of $15.8m (£8m).
The 42-year-old Bonds, whose career has been dogged by doping allegations, has 734 career home runs and is just 21 short of Hank Aaron's all-time record.
Earlier in the week he said: I knew things would work out - this is where I've always wanted to play. San Francisco is what I love.
"There's no better place to play than in San Francisco. This is my history and the people in San Francisco deserve it all."
Bonds, who has been with the Giants for 14 years, recently came to the end of a five-year $90m contract.
After missing all but 14 games in 2005 following three operations on his right knee, Bonds batted .270 with 26 homers and 77 RBIs in 367 at-bats in 2006.
His personal trainer, Greg Anderson, spent three months in prison after being one of those convicted in the Balco steroid scandal which rocked American athletics.
Major League Baseball had no steroid testing program in place for most of Bonds' career, including the 2001 season when he hit a one-season record 73 home runs.
And at the start of the month, the New York Daily News claimed he had failed a test for amphetamines.
Bonds has always denied knowing using banned substances.