Australia's former World No.1 enters this week's Open Championship convinced he's on the path back to the top after falling to 18th in the rankings and going 14 months without a win – the second-longest drought in his illustrious career.

But Day finally has his mojo back and he puts it all down to Steve Williams.

The 31-year-old says he hasn't looked back after turning to the 14-time major championship-winning caddie before last month's US Open at Pebble Beach.

"Having Steve on the bag has settled things down, which is nice, and I'm back working on the right things on my game," Day told AAP ahead of Thursday's start to The Open.

"I'm very positive about where things are going for the first time in a long time.

"It's really about trying to, not rededicate myself, but get more structure back in my practice, back in the way that I go about preparing for tournaments and really have a lot more motivation to go out there and try to win again.

"I don't have to say it, I can actually feel it."

It's not like Day's been completely in the doldrums.

He's had five top-five finishes this year, including at the Masters and the Players Championship, and tied for eighth at the Travelers Championship three weeks ago.

But by his prolific standards of 2015 and 2016, when he won eight times, including the US PGA Championship before finishing second in his title defence, Day feels he has "seriously under-achieved".

RIGHT: Day has changed putters ahead of the Open Championship. PHOTO: Rob Carr/Getty Images.

Hence why after alternating between former schoolmates Rika Batibasaga and Luke Reardon since taking his long-time coach Colin Swatton off his bag in late 2017, Day lured Williams out of retirement.

The 55-year-old former looper of Tiger Woods, Adam Scott, Greg Norman and Raymond Floyd is the most successful caddie in history.

"I've been around him enough to know him, but the experience he brings and obviously with the players he's caddied for, it's really comforting to be able to have that experience on the bag," Day said.

"And he's very positive so I'm very excited about our future together. Hopefully it's a long one. It's up to him. It's definitely up to him. We'll see how it goes.

"I've just got to keep busting my gut and I know that the results are going to come at some point.

"I've just got to be patient with it and let it happen."

Day hopes it happens at Portrush and says a change of blade has him feeling much better on the greens.

"I was getting a little frustrated with how things were progressing with my old putter and I feel like my aim is a lot better," he said.

"I changed it at home last week. I can trust it a little bit better, which is nice. I can just go and putt instead of worrying about where I'm aiming."

- Darren Walton, Australian Associated Press