Saluting his maturity, Jason Day's trusty lifelong coach is adamant the gifted former world No.1 has the game to finally shed his tag as a one-major wonder.

This week's PGA Championship in North Carolina marks the 10th anniversary of Day's record-breaking 2015 triumph at Whistling Straits - as well as a 53rd opportunity to add an elusive second major to his decorated CV.

In a career dogged by injuries and painful near misses, Day boasts an another incredible 17 top-10 finishes at golf's four biggest events.

As recent as 2023, the Queenslander joined one of the sport's most exclusive clubs that houses names like Jack Nicklaus, Tiger Woods and Phil Mickelson when he completed a grand slam of runner-up finishes at the majors at Muirfield.

Last month, Day tied for eighth at the Masters despite his revered world-class putting game deserting him at Augusta National.

The 37-year-old's resurgence, even while juggling life as a father of five, begs the obvious question: can he jag another major.

Col Swatton, the father figure who carried his bag at Whistling Straits when Day out-duelled then-world No.1 Jordan Spieth down the stretch to record the lowest-winning total in PGA Championship in history, has no doubts he can.

"Will it be this week at Quail Hollow? I don't know. Nothing would surprise me," Swatton told AAP on Tuesday.

"He won there in 2019, came close in 2017 when Justin Thomas went on to win it.

"Yeah, Jason definitely has the the skill set to get it done.

"We've made some pretty good progress this year. We've seen some signs. We saw it at API. We saw it again at the Masters.

"I've definitely seen the signs that I need to see to feel encouraged, and I think Jason's seen the signs that he's seen to feel also encouraged.

"Whether it's this year or not, I definitely think he's got another one in him, if not more."

It was not long after Day "went close", as Swatton put it, at Quail Hollow eight years ago that the pair split.

Day was only one shot off the lead with one hole remaining in round three before he ignored Swatton's advice to take his medicine after driving his tee shot to behind a tree en route to an infamous quadruple-bogey eight.

"(Hole) 18 on that Saturday cost us a lot in regards to being within striking distance to try and get another one," Swatton recalled after revealing why he reunited with Day earlier this year.

"He's obviously matured a lot," Swatton said.

"There's a lot that's happened in that interim period.

"He's changed coaches, he's gone to sought-after Chris (Como) and he's gone through everything that he needs to do to try and get some answers and clarify what's going on and and the best way for him to feel that he needs to swing it.

"Subsequently he's come full circle again. When he he reached out at the start of the year, he was honest ad saying 'Hey, I'm a little lost here'.

"Jase just needs to, and in his own words, quieten the noise that probably he's been going through for the last sort of three or four years, and also get back to the things that have made him great.

"So part of my job is to come back in and say, 'Hey, this is what you did when you were the best player in the world' and remind him of that."