After holing his second shot from just under 100 yards at the par-four 11th, his second hole at Pebble Beach, Oosthuizen raised his arms in triumph and broke into a broad smile before high-fiving his caddie.
One could hardly ask for a better start to a major championship, and he parlayed it into a five-under-par 66 to share the first-round clubhouse lead with Americans Rickie Fowler and Xander Schauffele.
"You can't see the second shot where it lands. I just went on the reaction of the crowd that it was a good shot and obviously saw that they went nuts," Oosthuizen said.
As if that eagle was not enough heroics for one day, he also holed a 50-foot sand shot for birdie at his final hole, the par-four ninth.
"I was fortunate with the uphill lie in the bunker, I could get some height on the ball and just try to get it within four or five feet right of the hole ... and it came out perfect," he said.
Oosthuizen is never happier than when at home driving a tractor on his family farm in Western Cape province, South Africa.
But he could reap something special on Sunday when, with a victory, he would join Jack Nicklaus and Tiger Woods as the only players to win a U.S. Open at Pebble Beach and a British Open at St. Andrews.
With an enviable swing that never seems to lose its rhythm, the 36-year-old has been a regular contender at major championships over the past decade.
He demolished the field at the home of golf for a runaway seven-stroke win at the British Open in 2010, and has frustratingly also finished runner-up in all four of the biggest championships.
Oosthuizen said that as much as he would love to win at Pebble Beach, he was not about to get picky.
"Just winning a U.S. Open would be very magical to me," he said, adding that he liked his chances if his putter co-operated.
"I feel I'm really a good driver of the golf ball and I can give myself good opportunities, and my iron play is pretty decent," he said.
"It's all on if I'm making putts on the week or not."
(Reporting by Steve Keating; Writing by Andrew Both in Cary, North Carolina)
