Maybe it was the glare off the trophy, or the flashbulbs popping and distracting in the early New York evening. But as the question came in at the winner’s press conference I was convinced there was a brief flash of anger in Brooks Koepka’s eyes.

It had been a marvellous effort to defend his US Open trophy, a culmination of the improbable at Shinnecock Hills given the wrist injury that had blunted his early season and forced him to miss the Masters.

He’d been methodical, at times swashbuckling, and ruthless.

Even at this moment of triumph, though, the American recognised a sense of under-appreciation.

“I always feel like I’m overlooked,” he declared. “I couldn’t care less. It doesn’t bug me. I just kind of keep doing what I’m doing, keep plugging away, kind of hide behind closed doors sometimes.”

Yet his body language, to me at least, revealed something different.

There was a touch of resentment – a frustration that the plaudits that should rightly be his still aren’t coming his way.

It’s all the stranger because something happens to Koepka during a major week.

The focus narrows, the concentration rises and everything matters more than the humdrum day-to-day.

Brooks Koepka

“There’s a lot more focus that I have in the majors,” he explained. “I mean everyone on my team even says I act a little different, the way I approach it.

“It’s very down to a routine this week and it’s much more disciplined. Eating right, going to the gym, it’s almost timed perfectly.”

For a career that has reached stratospheric levels so quickly, Koepka’s major record is insanely good.

Even if you take out the two US Open crowns, there are still another five top 10s and a further five top 20s in the big four events. This week’s PGA is only the 20th major in which he has competed.

He may claim not to be bothered about it, but the 28-year-old is criminally overlooked.

He was 25/1 with some bookies before the start of this tournament. When Jordan Spieth was carving a similar swathe a couple of years ago, you were lucky if you got near a quarter of those odds.

It can’t be about the way he plays. Koepka overpowers a course, combining devastating length off the tee with an arrow-like short game.

When he sees an opening, he doesn’t hesitate. It is brutally effective.

He took Bellerive’s front nine apart on Saturday, dispatching the challenge in just 30 shots. Yet while he was dismantling the St Louis layout, most of us were fawning over Tiger’s latest renaissance.

The crowds cheered every green the GOAT hit like it was his elusive 15th major.

Brooks Koepka

When Koepka speared another short iron into the heart of the 10th, however, there was little but polite applause. He is respected, but he’s not loved.

Is it because he appears indifferent on the course and detached in a way that maybe only a late 80s Nick Faldo could appreciate?

He allows nothing to get under his skin. There’s something almost robotic about the way he goes about his task.

His demeanour doesn’t excite spectators, even if his game does. Nor does he live for golf in the way some of us might expect. But they are our problems, not his. We should be marvelling at his talent, not casually letting it pass us by.

Had he not shown glimpses of humanity when bogeying the 14th, his first in 43 holes, and then the next, this tournament might already be over.

But does anything faze him? What may have turned into a full blown crisis for many was repelled with an iron par at 16 and a comfortable birdie at the penultimate hole.

I’m not sure he’ll give up his two shot lead on Sunday. And, with victory, Koepka would add his name to a very exclusive club.

One that comprises Sarazen, Hogan, Nicklaus and Tiger – the only players to win the US Open and the PGA Championship in the same season.

It might be hard for some to recognise it, but they are only kidding themselves.

Koepka will deserve to be in their company.