Danny Willett’s downward spiral since his Masters triumph has taken another bitter twist: He has been fired by his caddie.

Jonathan Smart, who was on Willett’s bag when he shocked the golfing world with his Augusta triumph 13 months ago, walked out on the golfer after a blazing tournament fight.

Willett accused Smart of giving him a bad yardage at the RBC Heritage event in South Carolina last month, the week after he missed the cut trying to defend his Masters title.

Smart responded by saying he was fed up with being a constant scapegoat when things went wrong on the course.

He packed his bags after the first round of the Heritage and flew home to England, forcing Willett to turn to a member of his management team to caddie.

Willett, 29, missed the cut there, too — the third time he has suffered that fate in his last five outings.

He will play for the first time since the bust-up at this week’s Players Championship in Florida.

Their rift is even more surprising as they have been pals since they were 13. Smart began working for Willett in 2010, and they seemed inseparable. The pair talked in glowing terms about each other’s qualities in a BBC documentary aired during the buildup to this year’s Masters.

Their split was the talk of the locker room at last week’s European Tour event, with players and caddies in disbelief that such a close partnership was over.

Willett will have another boyhood friend on his bag at Sawgrass this week: Sam Haywood, who was best man at his wedding four years ago.