They had a one-shot lead over Paul Casey and Charl Schwartzel on a day that started nasty and ended with 39 players breaking par. The biggest question after a long day on the links was what was in store for Friday, when high wind and occasional showers were in the forecast.
"I thought today's round was extremely important, as they all are," Spieth said, atop the leaderboard at a major for the first time since last year's Masters. "But given the forecast coming in, I thought you really needed to be in the red today. You can certainly make up ground in a round tomorrow, and we'll see it happen. But being able to kind of play with shots, or play a little more conservative because you don't try to do too much on a day like tomorrow, that's nice and very helpful."
Dustin Johnson and Rory McIlroy fall into that category.
Johnson, the No. 1 player who hasn't played the weekend at a major since the British Open last year, managed only one birdie on a decent day for scoring and shot 71. McIlroy also shot 71 and was relieved. Coming off three missed cuts in his last four events, he was 5 over through six holes when his caddie gave him a pep talk. McIlroy closed with three birdies over the last four holes to stay in the game.
Phil Mickelson failed to make a birdie, the first time that has happened in a major in five years, and shot 73.
Kuchar was the only one at 65 who played in the afternoon. The wind remained strong, though the course was manageable for everyone who stayed out of bunkers and deep grass and who holed putts.
"I watched some of the golf this morning on TV. It looked awfully challenging," Kuchar said. "It looked like anything under par was going to be a good score. Seemed like the later your tee time, the better draw you got. ... For me, to start my British Open with a 29 on the front nine is a great way to start."
Charley Hoffman had the best start of all, holing out from the rough on the daunting opening hole for an eagle. He was poised to join the leaders when he reached 5 under with a birdie on the 15th, only to drop shots on the next two holes. Hoffman shot 69 and was in a group that included Ian Poulter and Rafa Cabrera Bello.
Defending champion Henrik Stenson, who played with Spieth, had a 71. Stenson also played with Spieth the first two rounds of the 2015 Masters that the Texan won wire-to-wire and knew what to expect.
"He was rolling it superbly that week, and I don't think it was that far behind today," Stenson said.
But his best shot was with his feet in the sand. Spieth was in thick rough to the right of the 16th fairway when his shot crept into the back of a pot bunker. Not only was the ball on a slight slope, the rake marks left his ball between two ridges.
"This is dangerous," he said to his caddie.
He aimed to the right of the hole to avoid it going off the green on the other side and into another bunker, and it came off perfectly about 10 feet away.
"That was awesome," were his next words to his caddie.
He made the par putt - Spieth made a lot of putts on picked up a two-putt birdie on the 17th and narrowly missed a 7-foot birdie putt on the last. It was his best start in a major since he shot 66 at the Masters a year ago. Spieth rated it among the top five or six rounds he has ever played in a major, not bad for someone who came close to the Grand Slam two years ago.
"I couldn't have done much better today," he said.
Royal Birkdale was much more kind than it was nine years ago in raging wind and rain. The 146th Open began in cool temperatures, a light rain and a strong wind. Mark O'Meara, a winner at Royal Birkdale in 1998 who is playing in his last British Open, hit the opening tee shot.
And then he hit another one.
O'Meara's first shot was lost in the gorse, he made a quadruple-bogey 8 and was on his way to an 81. His threesome required 18 shots to play that hole. But the weather settled down a few hours later, and the scorecards filled up with plenty of birdies and eagles.
Just not for McIlroy until late in the round, or Johnson and Mickelson all day.
"With the weather we're expecting tomorrow, I still feel I'm in the golf tournament," McIlroy said. "If I can go out and play a good, quality round of golf in the morning and try to get in the clubhouse somewhere around even par, under par, I'll still be around for the weekend."
