Golf: How American veteran Phil Mickelson defied Father Time to create history

American star Phil Mickelson has overcome significant physical and mental barriers to become golf's oldest Major winner, leaving fans asking how on earth did he do that?

At 50 years of age and ranked only 115th in the world, his best days seemed behind him.

But Mickelson has turned back the clock to produce the moment of a career spanning more than three decades, with a two-shot victory that challenged the world's best at the PGA Championship in South Carolina.

Former Kiwi pro Phil Tataurangi played with Mickelson during his career and has remained in touch with him in recent years.

"He's basically defied Father Time," Tataurangi tells Newshub. "A lot of players that get to that age and that stage throw their hands up and say 'my best is behind me’.

"He's gone out of his way to lose weight and change his diet. He had arthritis that affected him in his mid 40s and realised he needed to change his physical regime.

"He's worked out like a beast, increased his swing speed and done everything he could possibly try with his golf swing to remain relevant in the game.

"For a long time, everyone said 'nice try, Phil, age is catching up with you', but he had his day in the sun today."

Now a six-time Major winner, Mickelson hadn't managed a top-10 finish in five years nor a PGA Tour victory in more than two. 

His latest success leaves him a US Open win away from a career grand slam - he's finished runner-up six times and the 2021 tournament looms next month.

Even with golfing muscleman Bryson DeChambeau in the field, Mickelson somehow managed the longest drive of the week - 366 yards off the 16th tee - but many of his lifestyle tweaks are as much mental as physical.

"I think some of the stuff he's been working on in the realms of coffee for wellness, fasting and changing his diet has been based around improving his mind," says Tataurangi. "He's basically figured that to be at his peak, he needs to be absolutely sharp.

"He mentioned it all week that his focus was waning, and he had trouble holding it for 18 holes or four consecutive days. It was a different Phil on the golf course over the last couple of days.

"He's always been the crowd favourite and always been jovial with the crowd, but it seemed like he was a little withdrawn and introspective, and spent a lot of time focusing on being present.

"The absolute most important shot was the next one, he forgot about the last one and over the four days, he outlasted a whole heap of young guys."

Mickelson has eclipsed American Julius Boros, who was 48, when he won the 1968 PGA Championship.

Jack Nicklaus won the last of his 18 Majors at 46, just a month younger the aptly named 'Old' Tom Morris, who the British Open in 1867.

"This might be the ride-into-the-sunset moment or it could spark something that continues for a few years yet," observes Tataurangi.