Golf legend John Daly says he has undergone a procedure to treat bladder cancer ... but doctors told him there's a high probability it returns.
54-year-old Daly -- who famously won the PGA championship in '91 -- says he had been battling back pain and kidney stones in recent weeks.
But after he passed the stones, Daly was still experiencing pain and doctors ultimately determined he had cancer.
"[The urologist said] it doesn't look like any stones are in there. But unfortunately, you have bladder cancer," Daly told the Golf Channel.
"After I did the CT [scan] I was fixing to sip on my Diet Coke and he said, 'Don't drink anything.