Phil Mickelson considered betting on Team USA to win the Ryder Cup – and lost $100 million gambling, book says

• Phil Mickelson racked up $100 million worth of losses gambling, according to a new book by Billy Walters.
• The golf star also tried to bet $400,000 on Team USA at the 2012 Ryder Cup, Walters wrote.

Phil Mickelson has bet over $1 billion over the past three decades, racked up $100 million worth of losses, and once considered placing a wager on Team USA winning the Ryder Cup, according to a new book.

Legendary sports bettor Billy Walters makes the claims about Mickelson in his upcoming autobiography, "Gambler: Secrets from a Life at Risk".

"Based on our relationship and what I've since learned from others, Phil's gambling losses approached not $40 million as has been previously reported, but much closer to $100 million," he writes in an excerpt published Thursday. "In all, he wagered a total of more than $1 billion during the past three decades."

Walters adds that in September 2012, Mickelson asked him to place a $400,000 bet on Team USA to win the Ryder Cup – a tournament Mickelson was playing in — but he refused, asking the former World No. 2 whether he'd "lost [his] fucking mind".

Europe subsequently pulled off one of the greatest comebacks in the tournament's history, winning eight matches and tying one on the final day in what's come to be known as the "Miracle at Medinah".

Mickleson denied ever betting on the Ryder Cup.

"While it is well known that I always enjoy a friendly wager on the course, I would never undermine the integrity of the game," he said in a statement responding to Walters' claims Thursday.

Walters said that he met Mickelson in 2006 and established a 50-50 betting partnership with the golf star in 2008.

Their relationship ended in 2014 – and three years later, Walters was sentenced to five years in prison and fined $10 million for insider trading shares in Dean Foods.

Prosecutors in the trial said Walters had illegally passed tips to Mickelson, who was never charged but was questioned by the FBI and had to repay around $1 million.

Walters denied ever passing information about Dean Foods on to Mickelson, and said the six-time Major winner had betrayed him by refusing to say that publicly.

"Phil Mickelson, one of the most famous people in the world and a man I once considered a friend, refused to tell a simple truth that he shared with the FBI and could have kept me out of prison," he writes in Thursday's excerpt. "I never told him I had inside information about stocks and he knows it."

"All Phil had to do was publicly say it. He refused."

"The outcome cost me my freedom, tens of millions of dollars and a heartbreak I still struggle with daily," Walters said.