Phil Mickelson has turned to swing coach Butch Harmon in a bid to improve the accuracy of his long game.
The three-time major champion is keen to work on his driving and has turned to Harmon, who has previously coached Greg Norman and Tiger Woods.
"Butch is one of the very best teachers in the world," said Mickelson.
"He's helped two players rise to number one in the game and I'm fortunate that he has agreed to spend time working with me, particularly on my driving."
Mickelson blew a superb opportunity to win last year's US Open at Winged Foot with a wayward tee shot at the last.
Harmon and Mickelson worked together on the practice range at the WGC-Accenture Match Play Championship in February and also at last month's WGC-CA Championship.
Mickelson had previously worked with Rick Smith for most of his career.
"This has been a difficult decision for me," said Mickelson. "Rick has worked with some of the best players in the game and his teaching was very instrumental in most of my 30 PGA Tour wins, especially my three major wins.
"I feel that now is the time to go in a new direction with Butch Harmon on my long game.
"I went to Rick as a friend and asked for his understanding of this decision and he's been very supportive of it. No one could ask for a more true or loyal friend."