UNIVERSITY PLACE, Wash. (AP) — One day after he collapsed from a bout of vertigo, Jason Day was standing taller than ever Saturday in the U.S. Open.

When the medication began to wear off and the vertigo returned, Day fought his way to the finish with a 31 on the back nine for a 2-under 68. He wound up in a four-way tie for the lead with Masters champion Jordan Spieth, Dustin Johnson and Branden Grace of South Africa.

Day felt nauseous over the final hour. He had to steady himself to stick a tee in the ground and pluck a ball out of the cup. And he considered quitting three times.

Good thing he didn’t.

The 27-year-old Australian is playing in the final group of a major for the first time.

“That was the greatest round I’ve ever watched,” said Colin Swatton, his caddie and longtime coach who whispered words of encouragement along the hilly terrain of Chambers Bay. “I said, ‘You’ve got the heart of a lion. You get to show the world today you get to be the greatest you can be and look, let’s do it.’ And he just put his head down and kept walking, one foot in front of the other. It was pretty impressive.”

Day steadied himself with a performance that brought to mind Ken Venturi winning the U.S. Open at Congressional in 1964 with a 36-hole final while suffering from heat exhaustion and severe dehydration, and Tiger Woods winning the U.S. Open at Torrey Pines in 2008 with a shattered left leg.

Day still has one day to go and a course that is getting faster and scarier by the day. And he has plenty of company.

Spieth, trying to become only the fourth player since 1960 to win the first two legs of the Grand Slam, squandered three birdie chances late in his round and had to settle for a 71. Johnson twice smashed driver that set him up for birdies down the stretch, and he couldn’t convert in his round of 70.

Grace overcame a rough patch in the middle of his round — three bogeys in five holes — and shot a 70.

Day wasn’t sure he would even play in the third round. He collapsed to the ground Friday in a frightening moment. He managed to get up with help, stagger into a bunker to play his next shot and made bogey to finish three shots out of the lead.

And then he delivered one of his best rounds considering the situation.

Day chose not to speak to the media out of sheer exhaustion. He offered a few comments to a USGA official, and then headed to his motor home to lie down.

“I didn’t feel that great coming out early,” said Day, who dropped two shots in his opening four holes to fall as many as seven shots behind at one point. “I felt pretty groggy on the front nine just from the drugs that I had in my system, then kind of flushed that out on the back nine. The vertigo came back a little bit on the 13th tee box, and then felt nauseous all day. I started shaking on 16 tee box and then just tried to get it in, really. Just wanted to get it in.”

He said it was worse than the vertigo he suffered last year at Firestone that caused him to withdraw. This time, he kept playing.

“I think the goal was just to go through today and see how it goes,” he said.

For everyone else, it was a matter of hanging on.

Spieth, Johnson and Grace each had the lead at one point on the front nine.

Spieth holed a pair of 35-foot birdie putts early and stretched his lead to three shots until he gave them back with a pair of three-putts, slapping his knee at the mistakes. He held on with some key pars, rolled in a birdie at the 15th to get back into a share of the lead, and then wasted three great opportunities — three putts from just off the 16th green for a par, a missed 10-foot birdie on the 17th and a 12-foot birdie putt that missed on the final hole.

“Just need to limit the mistakes tomorrow,” he said.

Johnson built a two-shot lead early on the back nine, only to give it back with a double bogey on the 13th hole with a poor second shot into the bunker. His tee shot on the 372-yard 16th hole landed near the front of the green, but three putts from the back forced him to settle for par. He also was in prime position in the fairway on the par-5 18th only to find a bunker.

Louis Oosthuizen, meanwhile, set himself up for a shot at U.S. Open history. No one since World War II has ever shot 77 in the first round of the U.S. Open and gone on to win. Oosthuizen was part of that horror show with Tiger Woods (80) and Rickie Fowler (81) in the opening round. He figured he would be watching the weekend at his home in Florida. Instead, he shot 66 to make the cut. And then the South African shot another 66 on Saturday and was at 1-under 209.

Cameron Smith of Australian had a 69 and joined Oosthuizen at 209, along with Shane Lowry of Ireland (70) and J.B. Holmes (71).

The number of players under par kept dropping — 25 after the first day, 16 after the second, now only eight going into the final day.

Rory McIlroy was losing hope in this major. He shot a 70 and was at 4-over 214. Phil Mickelson, meanwhile, lost another bid at the career Grand Slam with a 77 that put him at 10-over 220.