It’s been 14 years since a fresh-faced Rory McIlroy won his first-ever major championship at the 2011 US Open in Bethesda, Maryland. Since then, the PGA Championship, the Open and finally in April of this year, the Masters have followed, but none of it might’ve happened at all if a fellow professional hadn’t told McIlroy he needed to shed a few pounds.

Rewind to the early part of McIlroy’s career, and he didn’t cut the same lean figure he does today. And it was during a conversation with fellow golfing great Gary Player that McIlroy realised it was time to change.

Recalling the meeting, Player told The Daily Mail in 2016: “You need to get fit Rory, look at that weight you’re carrying [is what he said to McIlroy while pinching his belly]. You need to strengthen your core.”

It might seem like a cheeky dig, but there’s method behind the madness. A strong core can be key to a professional golfer’s performance, given the need to generate power for the booming drives and the steadiness that’s needed for under-pressure putts.

McIlroy headed the advice, got into shape and never looked back. Commenting on the Northern Irishman’s changed physique, Player said nine years ago: “I think he has the best swing in the game and that commitment to fitness will prolong his time as one of the best players around.”

It’s certainly something that McIlroy has continued to focus on throughout his career, and while he might’ve had to wait a little longer than he’d hoped to secure a maiden green jacket, his physicality is a key component in his success. However, after effectively completing golf by winning the career slam, McIlroy has since revealed it’s the mental side of the game he’s struggling with more.

Speaking ahead of this week’s US Open, the 36-year-old said: “You dream about the final putt going in at the Masters, but you don’t think about what comes next. I think chasing a certain goal for the better part of a decade and a half, I think I’m allowed a little bit of time to relax a little bit. But here at Oakmont, I certainly can’t relax this week.”

He added: “I think it’s trying to have a little bit of amnesia and forget about what happened six weeks ago. Then just trying to find the motivation to go back out there and work as hard as I’ve been working. At some point, you have to realise that there’s a little bit more golf left to play this season, here, [the Open Championship at] Portrush, Ryder Cup. So, those are obviously the three big things that I’m sort of looking at for the rest of the year.”

The US Open gets underway from Oakmont Country Club in Pennsylvania on Thursday.