Two-time U.S. Open champion Ernie Els believes mammoth courses such as Erin Hills could soon be commonplace due to players hitting the ball further than ever.
The venue for this week's major championship played at a huge 7,845 yards for Thursday's opening round - making it the longest track in U.S. Open history.
Rickie Fowler made light of the course's length to shoot a seven-under 65 and lead by two, while veteran South African Els - the champion of 1994 and 1997 - also fared well on day one, reaching four under through 16 holes before two closing bogeys took the shine off his round.
Addressing reporters after completing his day's work, the 47-year-old offered his thoughts on the changing nature of U.S. Open sites.
"I think we're in an experimental phase with the game of golf," said Els. "I played a practice round with a kid from Texas A&M, and he was hitting the ball 340 yards. I used to be one of the longest...hitting at 290.
"These type of golf courses might be the future: 8,000 yard golf courses. Technology helps when you swing the club very fast, and all of these youngsters are swinging the club at 120 miles per hour. So it could be the future.
"I know from my friends who are members at Shinnecock [Hills, next year's U.S. Open venue], the whole golf course has been moved back. So we're probably going to be walking 200 yards back to tees from the greens at Shinnecock, so that's how quickly the game has changed. This could be the future. Who knows?"
Els was delighted to be playing "pain-free" on Thursday, having been blighted by injuries in 2017.
"The way I've been scoring has been awful this year. But physically I wasn't great," he explained.
"A lot of times I had a couple of niggles ... the lower back, hip, shoulder and knee. It's really the first year that I've got experience with that, so it's kind of new.
"I feel good this week. I've got my trainer Vern here, and I'm feeling a bit better. I'm feeling really loose. That's been nice. It's nice to play pain-free.
"I felt that some of my game is coming back. My putting's back and short game's pretty good. So I've just got to play golf."
Fowler remained clear at the summit as the afternoon wave took on Erin Hills, although Australia's Marc Leishman moved into a share of second at five under through 13 holes.