By Mark Lamport-Stokes AUGUSTA, Georgia (Reuters) - Four-times major winner Raymond Floyd knows a thing or two about mental toughness in golf, when the pressure is at its most intense, and that is the one quality he admires most in Masters leader Jordan Spieth. American young gun Spieth was a runner-up and then champion in his first two starts at Augusta National and he launched his title defense in impressive style on Thursday by shooting a bogey-free 66 in tricky gusting winds. Now aged 22, Spieth won the Masters and U.S. Open last year before ending a stellar PGA Tour campaign with a total of five titles and an array of other awards while his brilliant putting already ranks among the best of all time.
