article: Media playback is not supported on this device The pair have been friends since their teens but had a disagreement during April's RBC Heritage event, with Willett eventually missing the cut. Smart felt mistreated and left his role, "effectively sacking" Willett, 29, mid-tournament, according to BBC golf correspondent Iain Carter. "Things are a bit stale and kind of fizzled out," Willett told BBC Sport. "It is a shame. But things happen and change, everything happens for a reason. "We are still working hard to get the game in shape to get back playing the golf we know we can play." Willett did not rule out the prospect of his childhood friend one day returning to his bag but he was forced to use a member of his management team in the second round at the RBC Heritage. He will use Sam Haywood at this week's Players Championship in Florida. Haywood was best man at Willett's wedding and has recently been on the bag of American player David Lipsky. "Sam knows my game really well," Willett added. "We've played a lot of golf together over the last 10 or 15 years. It's nice having someone who you can speak frankly with. He knows where my game is and when it's good. I think it's going to be good." Smart and Willett memorably embraced in the recorders' room at last year's Masters when it became clear the Englishman had won a first major. But he has not won a tournament since, placing outside the top-25 in the three other majors in 2016 before missing the cut on his return to Augusta in April. The dip in form has seen him fall 10 places to 21 in the world since the turn of the year. BBC golf correspondent Iain Carter It's been a struggle to adjust to the status of a major champion for Willett. Results haven't been good for a year. Recently he's missed three of the last four cuts, so these are trying times. It came home for me today as I remember this day last year I approached him at his first tournament since winning the Masters. Now, the mood music could not be any different.
summary: Danny Willett has split with caddie Jonathan Smart just over a year after winning the Masters at Augusta.