The R&A's engraver might even have started scratching the champion's name on the Claret Jug late on Saturday night.
A two-time major championship winner, Spieth held a three shot lead over serial non-major winner Matt Kuchar and the next-nearest challenger was fully six strokes adrift.
Victory, and another step towards golfing glory, seemed inevitable.
Then Spieth teed off and his challenge quickly went horribly wrong.
Spieth had rocked up to Royal Birkdale in fine form and apparently set to resume his assault on the record books.
At the time he had played the Masters four times, winning once and finishing second twice.
His victory at Augusta National had come in 2015 and he followed it up with another Major win in the US Open at Chambers Bay.
He then fell one shot outside a play-off on The Old Course at St Andrews in the British Open and was solo second in the PGA Championship at Whistling Straits.
In other words, he had been a mere handful of shots from completing the Grand Slam.
Further Major success had eluded him, most famously when finding water at the 12th hole in the 2016 Masters, but he continued to prove himself a prodigious winner.
In fact he'd raised his PGA Tour win to ten the week before crossing the Atlantic at the Travelers Championship.
That victory had been completed in style, holing out from a greenside bunker on the first extra hole to prompt ecstatic scenes around the green.
"A pretty ridiculous roar," he said. "As loud as anything I've created."
The excellent form was maintained on Thursday as he carded a 5-under-par 65 that left him tied at the top of the leaderboard alongside Kuchar and Brooks Koepka, who had won the US Open the previous month.
"I couldn't have done much better today in 15 mph crosswinds," he said. "I missed only three greens, but one of them I was putting from the fringe."
He noted that he'd had trouble from the 13th tee, missing the fairway on the right into the dunes where a spectator trod on the ball and he needed a free drop.
It was not the last time the hole would feature prominently in Spieth's week.
A 69 on Friday gave him a one-shot advantage and a 65 in perfect conditions (Branden Grace carded the first sub-63 in Major Championship history) extended that gap to three.
It was the 10th solo 54-hole lead of his career and he had converted seven of the previous nine.
There was only one Major champion within seven strokes of his lead.
A done deal?
A remarkable Sunday
The leader opened the final round with three bogeys in his first four holes and was suddenly tied at the top with Kuchar.
A birdie-bogey exchange at the sixth saw Spieth sneak two clear, but the roles were reversed at the ninth so they made the turn locked at 8-under-par and stayed that way through the 12th.
The rest of the field was involved in nothing more than a scrap for third place.
At the start of the week 156 players had a chance. Now it was pure head-to-head stuff.
Quite literally so, in fact, from the 13th tee as Spieth's tee shot once again veered right towards the dunes where it bounced off a spectator's head and onto the far side of the sandhill.
When Spieth arrived at the spot he couldn't believe where the ball had finished.
It was lying in deep fescue grass on a slope almost impossible to stand on never mind hit a shot from.
What happened next displayed the bravado of the then-23-year-old. He'd never been one for playing golf along the straight and narrow, and he wouldn't be now.
Most contenders in the final round of a Major Championship visit the driving range before they tee off.
Spieth had already done that, but now he also decided to visit it in the middle of his round, opting to take his ball backward towards the equipment trucks that line the practice area.
His exchanges with the officials - to verify his actions - and with caddie Michael Greller - to determine the yardage of his next shot - took over 20 minutes.
That blow, his third on the par-4, fell shot of the green, but he got up-and-down for a bogey to slip one behind Kuchar.
"That was massive," he said, adding that the reversal at the top of the leaderboard had a paradoxical effect.
"Once I lost my lead completely I actually felt the nerves go away," he said.
Suddenly, after all the misfiring, he finally caught fire in sensational fashion.
At the par-3 14th he watched Kuchar hit a safe shot and then: "I hit 6-iron, 199-yards, like a laser, it almost went in."
Now tied for the lead and energised by the bounce-back, he powered on to the par-5 15th.
Kuchar made birdie-4, but Spieth found the front of the green in two, drained the putt for eagle and then pointed at Greller to fetch the ball from the hole.
Pumped, he holed from 30-feet for birdie at the 16th and made it 5-under through the four holes since the 13th with another par-breaker at the 17th.
Kuchar was broken and Spieth could afford a safe par at the last.
"I was so confident at the start," he said. "Then, all of a sudden, the wheels had come off.
"It was a question of how do we get back on track to salvage this round? What gives us a chance at the end?
"It took a bogey."