Mickelson denies betting on Ryder Cup despite claims of over $1B in wagers

Mickelson accused of placing over $1 billion in sports bets over three decades and losing around $100 million.
Book by gambler Billy Walters claims Mickelson wanted to bet $400k on 2012 Ryder Cup.
Mickelson denies betting on Ryder Cup, says he would never undermine integrity of the game.
Partnership between Mickelson and Walters ended in 2014; both involved in insider trading case.
Mickelson acknowledges past reckless gambling and addiction, says he has received therapy.