Phil Mickelson gambled more than $1 billion on football, basketball and baseball over the last three decades and attempted to make a $400,000 wager on his 2012 U.S. Ryder Cup team, according to excerpts from an upcoming book that appeared Thursday in the Fire Pit Collective.

Phil liked to gamble as much as anyone I've ever met, wrote renowned professional gambler Billy Walters in Gambler: Secrets from a Life at Risk, which is set to be released later this month but was excerpted Thursday in the Fire Pit Collective.

Frankly, given Phil's annual income and net worth at the time, I had no problems with his betting. And still don't. He's a big-time gambler, and big-time gamblers make big bets. It's his money to spend how he wants.

Walters also claimed in his book that Mickelson attempted to make a $400,000 bet that the U.S. team would win the '12 Ryder Cup. The Americans lost to Europe by one point at Medinah, with Mickelsons singles loss to Justin Rose contributing to the defeat.

Have you lost your f---ing mind? Don't you remember what happened to Pete Rose? You're seen as the modern-day Arnold Palmer. You'd risk all that for this? I want no part of it, Walters wrote. He added that he didnt know if Mickelson made the bet elsewhere.

Walters cited betting records and two very reliable sources that Mickelson made 858 bets of $220,000 and 1,115 bets of $110,000 from 2010 to 2014. He estimated that Mickelson lost about $100 million, while betting more than $1 billion over the past three decades.  

Walters first met Mickelson at the 2006 AT&T Pebble Beach Pro-Am but their relationship unraveled in 2014, when federal authorities began looking into a series of stock trades that they each made. Mickelson refused to testify in an ensuing insider-trading case against Walters, and in April 2017, Walters was convicted on charges of conspiracy, securities fraud and wire fraud. He was sentenced to five years in federal prison. 

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, wrote Walters, whose sentence was later commuted by former President Donald Trump. 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.

Mickelson made more than $96.6 million in his PGA Tour career, and the six-time major champion also reportedly signed a multiyear contract with LIV Golf last year worth an estimated $200 million.

Golf Channel has reached out to Mickelsons representatives for comment. Mickelson is playing this week at the LIV event at Trump Bedminster in New Jersey. Asked by a reporter at Bedminster to comment, Mickelson replied, "I'm gonna pass today."