SOUTHPORT, England — Jordan Spieth is one round away from the third leg of a career Grand Slam and one year removed from a reminder that winning it won't be easy.
On the horizon is a chance to join Jack Nicklaus as the only players to win three different majors by age 23. Lurking in the past is his last time leading a major, when he let a five-shot lead get away from him on the back nine at last year's Masters.
All that mattered to him Saturday was the present.
Spieth did his part on an extraordinary day of scoring in the British Open, capping off his 5-under 65 in the third round by seizing on a good break and making a 20-foot birdie putt on the 18th hole for a three-shot lead over Matt Kuchar, who did his best to keep pace with 66.
Spieth had one of seven rounds of 65 or lower at Royal Birkdale, which was never more vulnerable with a light breeze and a clear sky until the final hour. Spieth was warming up on the range when Branden Grace shot 62, the lowest 18-hole score in major history. Spieth then delivered his second bogey-free round of the week, never coming seriously close to a bogey.
"Pretty stress-free," said Spieth, who led after the second round. "On a Saturday with a lead in a major, that's as good as I can ask for."
He was at 11-under 199, breaking by six shots the 54-hole record at Royal Birkdale that Tom Watson set in 1983. Not only did that last birdie give him a three-shot lead, no one else besides Kuchar was closer than six shots.
This will be Spieth's third time taking the lead into the final round of a major. He led by four at the Masters two years ago and won by that margin. More recent was a one-shot lead at the Masters to start the final round last year, a five-shot lead at the turn and a quadruple-bogey on the 12th hole that cost him another green jacket.
Spieth was embracing both memories.
"I think I'm in a position where it can be very advantageous, just everything I've gone through — the good, the bad and everything in the middle," he said. "I understand that leads can be squandered quickly. And I also understand how you can keep on rolling on one."
He described the Masters last year as a humbling experience that he thought would serve him well down the road.
"If I don't win (today), it has nothing to do with that," he said. "And if I win (today), it has nothing to do with that, either."
Kuchar will play in the final group of the fourth round at a major for the first time, and the 39-year-old, who hasn't won a major, sounded up for the occasion.
"It's not that I ever felt like I was playing Jordan (on Saturday)," said Kuchar, who was paired with Spieth on Saturday, too. "It's trying to go up against Royal Birkdale and put on the best show you can against the golf course."
Missing from the mix was Rory McIlroy, who looked to be a big threat when he began with three birdies in five holes, driving the green on the shortened par-4 fifth hole. He lost it around the turn, making back-to-back bogeys, and then double bogey at No. 10 when he blasted out of one pot bunker left of the fairway and the ball spun toward another, resting in the thick collar.
McIlroy had 69, rarely a bad score in the third round of a major. This one left him nine shots behind.
"I've always been good when I get off to fast starts, being able to keep it going, and I didn't (Saturday)," he said. "And I needed to. That's the disappointing thing."