"This one is going to test your resolve. Mental, physical, everything. So you're probably going to need a couple of days off after Sunday."
Those were the words of Ernie Els this week as he assessed the challenge posed by Oakmont Country Club, the venue for the first of his two U.S. Open wins way back in 1994.
'The Big Easy' is certainly not alone in expecting to face great difficulty at the second major championship of the year. Angel Cabrera won the last U.S. Open at Oakmont, nine years ago, with an aggregate score of five over - the sort of number many feel could be enough to secure success on Sunday.
Penal rough, even by USGA standards, is set to offer perhaps the greatest challenge to the 156-strong field, its severity prompting reigning champion Jordan Spieth to suggest: "I think if you're under par, you certainly win. I don't think it takes under par to win."
Commenting on the changes at Oakmont since his triumph, with a five-under total, Els said: "I would say they've really upped the ante the last five to 10 years with the rough. Whatever they call it, the graduation of the rough, whatever, it's just thick, and it's a lot more dense than it was.
"We could move the ball around. It was almost more fun to play that way because you could advance the ball, you could get the ball to run towards the green. You're not always going to hit the perfect shot, but you had a chance of actually hitting a shot.
"Now it's at least a half a shot penalty. You try to get a wedge out to where you can play your next shot from. That's just the way it is. They've really got the premium on accuracy and ball striking.
"It is what it is. Back in the day, it was a little different. We could manouevre the ball out of the rough."
World number one Jason Day highlighted the difference between Oakmont and most courses seen on the PGA Tour.
"We always say each and every week, it's a bomber's course. For the most part, it's a bomber's game, our generation. It's not like that this week," said the Australian.
"I played last Friday, and there was this shot that I hit 10 feet out of the rough. You just cannot hit it in the rough in certain places, and I don't want to do that."
Not that the rough, which Spieth describes as "really tough, but still fair", is the only obstacle to overcome in Pennsylvania this week.
Oakmont also boasts 210 bunkers, including the infamous 'Church Pews' on the third hole, fiendishly fast greens and the longest par three in U.S. Open history. The eighth hole is 288 yards on the scorecard and was played at 300 yards during one round in 2007.
"You're going to have stretches where you're going to have to try and survive, and it's going to happen to every player in the field," concluded Els.
"That is why this is the ultimate U.S. Open test at Oakmont."
Good luck, guys.