Adding to his season of woe, a persistent back injury affected his performance or forced him out of tournaments and he lost his PGA Tour card.
"At the end of 2016 I was in contention in the Race to Dubai and I just didn't want to play golf. It's utterly ridiculous," he wrote in a blog on the European Tour website (www.europeantour.com).
"I had entered the HSBC Champions in China, Turkey, Nedbank and Dubai – four of the biggest tournaments of the year – and I didn't want to play. I just didn't feel good enough to compete.
Willett's back trouble had got to a point where it was "taking over his game", he said.
"When I swing good, I feel good mentally and physically... when I was swinging badly, I was putting strain on my back and it became an issue.
"It was annoying as working out didn't hurt it, drills didn't hurt it but firing into the ball at full speed and just being a little off could cause a lot of pain.
"I'd be taking painkillers in the morning ... getting an hour of physio before each round, playing the round with a swing that hurt, then needing an hour of physio after the round. I was just knackered."
Willett sought suggestions from friends to improve his form and took solace from the fact that his possession of the famous green jacket would forever give him a place among the biggest names in the game.
"The Champions Dinner was an eye opener," he said.
"Sitting around a table full of these legends of the game, all telling stories of Arnold Palmer and Augusta, it inspired me and gave me the boost I needed to look for help.
"I look back on that dinner and tell myself there was a reason I had a name card and a place at that table. I had earned an invitation and I often find myself remembering that meal."
(Reporting by Shrivathsa Sridhar in Bengaluru, editing by Nick Mulvenney)
