Rahm was running away with the Memorial Tournament – leading by six shots after 54 holes – before having to withdraw and go into self-isolation but said on Saturday he was cleared to play after two negative tests in a 24-hour span.

The Spanish World No.3, in search of his first major, will be in comfortable surroundings on the South Course as he has four top-10 finishes in five events there, including a win in 2017.

Six-time runner-up Phil Mickelson missed the cut at the 2020 US Open but arrives this year brimming with confidence after winning last month's US PGA Championship – becoming the oldest major winner at the age of 50.

For Mickelson, a three-time winner of the PGA Tour event at Torrey Pines, the course he grew up on, this week offers him an incredible chance to become only the sixth person to complete the career Grand Slam of golf's four majors.

"It's a unique opportunity because I've never won a US Open," Mickelson said.

"It's in my backyard. I have a chance to prepare properly, and I wanted to put in the right work.

"It's a unique opportunity because I've never won a US Open. It's in my backyard. I have a chance to prepare properly, and I wanted to put in the right work." – Phil Mickelson

"So I've kind of shut off all the noise. I've shut off my phone.

"I've shut off a lot of the other stuff to where I can kind of focus in on this week and really give it my best chance to try to play my best."

Top ranked Dustin Johnson, who missed the cut at this year's Masters and US PGA Championship says his game is close.

World No.2 Justin Thomas and four-time major winner Rory McIlroy are among those in the 156-player field who will try to snap out of a form slump on a notoriously difficult layout with penalising rough.

Defending champion Bryson DeChambeau, who overpowered Winged Foot last year to win his first major by six strokes, comes into the year's third major having finished in a share of 18th place at the Memorial Tournament.

Brooks Koepka, who counts two US Open wins among his four major victories, may not be at 100 percent after surgery in March to repair a dislocated kneecap but has proven he can play through pain as he finished runner-up at the US PGA Championship.