In the lead and in the trees, he slashed a 7-iron toward the green and started barking instructions at the golf ball until he saw it bound onto the 14th green. He never saw it smack into the pin and settle a few feet away. He only heard one of the loudest cheers of the afternoon.
"What happened?" Spieth said to his caddie.
With six birdies in a seven-hole stretch, Spieth flirted with a major championship record he didn't know existed and atoned for his lone mistake with one last birdie putt for an 8-under 64. It was the best opening round at Augusta National in 19 years, gave him a three-shot lead and stole plenty of buzz from the Grand Slam bid of Rory McIlroy and the return of Tiger Woods.
"It's one of the better rounds I've ever played," Spieth said.
The day belonged to Spieth, a 21-year-old Texan who got into the Masters record book as the youngest to lead after the first round.
An even more significant record was within his reach, and he didn't even know it.
Spieth went to 8 under with that birdie on the 14th hole, and then he blistered a driver down the fairway on the par-5 15th hole, just 228 yards to the hole. That's when he started thinking about a 62 because he had never shot 10-under par as a pro.
But he hit hybrid over the green and wound up making bogey. Only later did Spieth realize that 63 was the best score in any major, and only two players had done at the Masters -- Greg Norman in the first round of 1996 and Nick Price in the third round of 1986.
Spieth was thinking about 62. He had never shot 10-under par as a pro.
"I wasn't aware what the course record was here, let alone that it actually would have been the lowest round in major championship history. So that's a little frustrating," Spieth said before he paused with a wry smile. "But I'm certainly OK with the day."
Spieth has stormed out to a three-shot lead over Ernie Els, Jason Day, Justin Rose and Charley Hoffman.
It wasn't that big of a surprise.
Spieth shared the 54-hole lead last year at Augusta with Bubba Watson until a four-shot swing over the final two holes of the front nine as Watson pulled away. Plus, Spieth might have been the hottest player coming into this Masters.
He won at Innisbrook in a three-man playoff. He was runner-up at the Texas Open. And he lost in a three-man playoff at the Houston Open just four days ago. The biggest challenge he faced was to keep his expectations from growing taller than a Georgia pine and to make sure he was plenty rested.
Whatever the formula, it worked.
"What a player," Els said after a 67, his best score at the Masters since the day Phil Mickelson beat him with a birdie on the final hole in 2004. "You just cannot see this kid not win many, many majors. I think he is by far the most balanced kid I've seen. Jordan, he's got that little tenacity to him and he's really got a fighting spirit, and he's the nicest kid in the world. ... He's a special kid."
Els played the par 5s in 5 under and briefly had the lead until Spieth went on his birdie spree. Hoffman finished with an eagle and two birdies over his last four holes.
"It's the coveted green jacket you want to get," Hoffman said. "I'm trying to approach it like if I get in position, I'm going to be aggressive. If I get out of position, I'm going to try to get back in position just like any other golf tournament."
Day looked to be the most dangerous. Twice a contender at Augusta in the past four years, he made five straight birdies on the back nine until he lost momentum with a three-putt bogey on the 17th. Still, three shots behind after one round wasn't a bad place to be.
Plenty of others took advantage of prime scoring conditions on a sunny spring day, the greens a bit soft even as the temperatures climbed into the upper 80s, with barely a hint of the breeze that can cause so much havoc.
Russell Henley, a Georgia native with plenty of fans in the gallery, turned in a 68. Bill Haas, Webb Simpson, Paul Casey and Ryan Palmer were at 69. Sergio Garcia was also in the mix at 4 under.
McIlroy, trying to complete a career Grand Slam after winning the final two majors of 2014, had a couple of sloppy shots but still shot 71. So did defending champion Watson, even though he admittedly tired down the stretch and lost focus.
Tom Watsonbroke par for the first time at the Masters since 2010 with a 71.
"It's fun to be able to at least be in red figures at Augusta National," Watson said. "At my age, it's a minor miracle."
If the 65-year-old can make it to the weekend this year, he would be the oldest player to make the cut at the Masters. Tommy Aaron was 63 when he made it in 2000.
"Old age and treachery," Watson said to explain his score. "I played the golf course enough times to know where I'm supposed to hit it and where I'm not supposed to hit."
Then there's Woods, returning to competitive golf for the first time since he walked off the course at Torrey Pines in early February, saying he needed to improve his game before he played again.
Woods clearly improved during the time away but doesn't yet seem capable of making a serious run at his 15th major championship. He struggled to a 73, leaving him nine shots behind Spieth going to Friday and more concerned with making the cut than contending for the lead.
Spieth leads Masters after first round
Jordan Spieth shot a 8-under 64 to hold an three-stroke lead. Tiger Woods finished with a 1-over 73.
Spieth happy with first round
Jordan Spieth recaps his first-round 64 and what it's like to be in the lead at the Masters.
Digital Drive: Who finishes better
ESPN golf analyst Andy North thinks Sergio Garcia and Bubba Watson will finish the 2015 Masters in a better position than Ernie Els and Tom Watson.