Phil Mickelson has won 42 times on the PGA Tour, including five major championships, but one victory stands out.
The Hall of Famer told David Feherty of the Golf Channel that his 2013 British Open at Muirfield was the best achievement of his 25-year career.
"It's the best," said Mickelson. "There's no better feeling, because I had a multiple-shot lead. I knew that if I made par on 18, that I would win, as difficult as the holes were playing coming in."
Mickelson started his final round five shots back of leader Lee Westwood, but a final-round 66 gave him a title few thought he had the game to conquer.
"The greatest accomplishment of my career, is winning The Open. My game was never suited to that, I liked hitting it high with the spin."
Mickelson's best finish at the British Open, prior to his win, was a tie for second in 2011 and the a third place finish in 2004.
"To ultimately win that tournament is the greatest feeling and accomplishment for me, because I learned and became successful at a totally different style of play."
The 46-year-old needs to win the U.S. Open to become just the sixth player in history to complete the professional career grand slam.