Cameron Smith admits chasing down the US Open leaders would require the “round of his life” after falling well back on the leaderboard in round three at Los Angeles Country Club.

Smith started moving day at four under par and with a chance at inching closer to the lead. But with six bogeys and five birdies, the consistency wasn’t there during a 71 that dropped him to three under.

“There was lots of good in there, but I think it was just the golf course was tough,” Smith said of the par-70 layout at LACC. “The golf course is getting firmer and faster, as I expected, and going to take some really good play to get around even, and managed to hang in there for a while and get under par before a poor finish, I guess, the last five holes.”

Sitting well back of the lead, Smith was asked if a victory was possible. He said nothing short of a 63 would be good enough. The last person to shoot 63 to win a major was Johnny Miller 50 years ago, at the 1973 US Open. Smith himself shot 64 to win the Open Championship at St Andrews last year from a four-shot deficit.

“Geez, probably [take] one of the best rounds of my life,” Smith said. “It’s going to have to take at least … 7-under (63). The golf course is getting tougher, but there’s still lots of wedges out there. The leaders are there for a reason, as well. They’re obviously playing really good golf.”

Min Woo Lee was the only other Australian to make the cut and also regressed, with a four-over 74 sinking him to two under. Lee started day three at six under and with a great chance to shoot his way into contention.

Meanwhile, New Zealand’s Ryan Fox shot a 69 on Saturday to improve to one over par. Given 65 players, an uneven number, made the 36-hole cut, Fox was slated to play by himself until the USGA gave the tap to director of golf at LACC, Tom Gardner, to play as the “marker” with Fox. Gardner had his head pro, Rory Sweeney, caddie for him. The pair marvelled at Fox’s power. He’s known as one of the DP World Tour’s longest drivers.

“Ryan is a good guy, hammers the ball, and we just had a good time out there, played pretty quickly,” Gardner said. “I love competing. I love playing golf. I’m not a [US Open] competitor, but to be able to say that I got to play a US Open setup on the weekend and see what it’s like and see the energy of the crowd and see the pins and the firmness and the rough and everything that goes along with it, it’s … I can’t really describe it. I’m hoping to do it all again tomorrow.”