San Francisco: Winning his first major title at the US Open on Sunday turned out to be far more difficult than Webb Simpson ever imagined.

The 26-year-old American triumphed by a single shot after a grueling afternoon at the Olympic Club and he was indebted to his caddie, Paul Tesori, for making sure he stopped watching the leaderboard early in the final round.

"I was glad Paul told me that because I've been a leaderboard watcher my whole life," Simpson told reporters after sealing victory at the year's second major with a two-under-par 68.

"With what pressure a major brings, I just didn't think it would do any good to see where I was at. So much can happen during the middle part of the golf course, so I didn't look again.

"The crowd was kind of telling me where I stood. They were getting louder and really pulling for me, which I appreciated. I putted out on 18 and that was the first time I looked (at the leaderboard) since early on the front nine."

Simpson began the final round at fog-bound Olympic four strokes off the pace and he teed off in the fourth-last group of the day.

Four birdies in five holes around the turn lifted him into contention but he then had to watch on television to see if overnight leaders Jim Furyk and Graeme McDowell could match his one-over total of 281 as they played the final two holes.

Nervous Television Watcher

"I was just as nervous watching on the telecast as I was playing," Simpson smiled. "They're such great players. Each of them has won a major. It was nerve wracking to say the least.

"I just gained so much respect for the guys who have won multiple majors, because it's so hard to do. The level of pressure is so much greater than a regular event.

"I don't know how Tiger (Woods) has won 14 of these things (majors) with that pressure. I couldn't feel my legs for most of the back nine."

Simpson has surprised even himself by how quickly he has won his first major title.

His maiden victory on the PGA Tour came late last year at the Wyndham Championship, in his home state of North Carolina, and he then clinched his second at the Deutsche Bank Championship soon after.

"I was kind of hoping for my first win on the PGA Tour last year, but to think my second would come just two weeks later I didn't," Simpson said.

"If I was honest with you I believed in myself that I could win a major, but maybe not so soon. This is only my fourth or fifth (major appearance).

"This is only my second U.S. Open and so I told myself, 'Don't get too excited, don't try to win. You've got to go out there and try to make pars.' That's what I did, and luckily I made some putts."