SAN FRANCISCO — KYLE STANLEY took a deep breath and exhaled. Then he took another — almost a sigh.

Hey, if you don’t think playing in this U.S. Open at the rugged, hilly and extremely demanding Olympic Club course will take it out of you — even if you’re a fit 24-year-old PGA Tour player — then you needed to walk 18 holes Thursday in Stanley’s shoes.

The former two-time Clemson All-American had just finished slogging his way around the deceptively long 7,170 yards, coming home at 3-over par 73 — not the day’s best round (that was long-shot Michael Thompson’s 4-under 66) but hardly the worst, either. Stanley played the roughest stretch of Olympic, the first six holes, in 2-over, which put him about even with, or a bit ahead of, the field.

“I played better than my score, I think,” the soft-spoken Washington State native said. “If you get out of position on these holes, it’s so easy to make bogeys. I feel like I putted well, made a lot of 3- and 5-footers.

“I was OK with that. Mainly, I was finally comfortable on the golf course, which was nice.”

Back when this PGA Tour season was young, the notion of Stanley being uncomfortable with his sport seemed unfathomable. He was arguably the Tour’s player of the month in January, when he experienced a lifetime’s worth of highs and lows in about eight days.

The final round of the Farmer’s Insurance Open, with his first Tour title seemingly socked away, Stanley suffered a final-hole meltdown: drowning his easy approach on the par-5, finishing with a triple-bogey 8 to blow a 3-shot lead, then losing to Hunter Mahan in a playoff. The sight afterward of Stanley in tears was haunting.

One week later, his psyche was whipsawed — in a good way. Trailing by eight shots at one point, Stanley overtook leader Spencer Levin, who suffered a similar fate as Stanley the previous Sunday. This time, Stanley won; again, he cried. Talk about an emotional roller coaster.

In retrospect, Stanley, since then was dealing with a mental hangover that — until this week — he couldn’t shake.

“My game hadn’t been that great, and I’ve been trying to find some confidence,” said Stanley, a resident of Berkeley Hall near Bluffton. He had shot a combined 31-under par those two weeks; in 12 tournaments since, he was 38-over par with six missed cuts and a best finish of a tie for 49th.

Stanley says now he didn’t realize how draining the Farmer’s-Phoenix fortnight had been. After a pair of decent finishes, he missed the cut at the Honda Classic, and “it starting going (bad).

“If I’m playing well, I work at it; if not, I don’t,” he said. “The biggest thing was probably my time management. At the end of the day, (his success) depends on how hard I work. I was probably just mentally tired and got a bit complacent” after winning.

The difference now might have less to do with who’s swinging the clubs and more to do with who’s hauling the bag. This week, Dave Woosley, a PGA Tour veteran and free spirit who practices yoga and Zen, and whose previous bosses included Champions Tour player Chip Beck, became Stanley’s third caddie of 2012, replacing Brett Waldman.

“It’s been good,” Stanley said of the switch. “(Woosley) has a different personality, very calm — very ‘chill,’ ” he said, flashing a rare smile. “The last couple of days, I’ve felt like the old Kyle, which is nice. I’m back to a good mental state where I can relax, enjoy what I’m doing.”

Relaxed is not something Stanley seems to do well. At Clemson, he projected a quiet, introspective and intense image. And where many former Tigers bond on and off the course, Stanley’s three years there now seem to have been merely preparation for what he’s doing now.

“I’m not like Lucas (Glover, the 2009 Open champion) or Jonathan (Byrd, with whom Stanley played Thursday),” he said. “I love Clemson, but I don’t pay that much attention to it” these days.

Indeed, his focus is on himself and his game. He missed 10 of 18 greens Thursday but held his game together. A clutch 3½ -foot, par-saving putt at the par-4 fifth — “if I miss that, I’ve got five feet coming back” — helped settle him.

Any fatigue he exhibited was because of Olympic, not his state of mind, Stanley said. And if an emotionally rocky Stanley could pull off his Phoenix comeback, imagine what a calm, clear-headed Stanley might do.

You got an idea how that might work when he was asked about playing with Byrd, a 10-year veteran and quiet personality, who shot a solid 1-over.

“Yeah, it was good. He’s a nice guy,” Stanley said.

He then added, almost under his breath, “He’s just such a jerk.” Checking out reporters’ reactions, he grinned slyly. “Just kidding,” he said. “I may have to play with him again.”

Physically, Stanley appeared a bit tired Thursday. Mentally and emotionally, he looked ready for whatever this U.S. Open, or the rest of his year, might throw his way.

Which, as he says, is nice.