June 25, 2015 6:26 AM EDT

Jordan Spieth is a math problem who wields a 3-wood. To win all four golf majors in a year, which no player in history has done, Spieth must beat more than 100 fellow pros over four days, on four different courses, in four different tournaments. The odds seem infinitesimal.

But why not a Grand Slam for Spieth, who clinched his first U.S. Open title on June 21, becoming the first golfer since Tiger Woods in 2002 to win the Masters and U.S. Open back-to-back? Spieth took the title after Dustin Johnson missed two putts on the 18th hole, handing Spieth a one-stroke win. That Spieth clearly felt bad for Johnson in his moment of defeat only adds to Spieth’s appeal. At 21, Spieth is preternaturally composed. His gifted game has already conquered two majors. Up next: the laws of probability.

–SEAN GREGORY

This appears in the July 06, 2015 issue of TIME.

Write to Sean Gregory at sean.gregory@time.com.

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