Fleetwood had to be content with runners-up spot, one stroke behind American Brooks Koepka, but Spieth said he could carry that momentum into Carnoustie when it starts on July 20.
"A 63 on Sunday, he had a few putts at 62 I know he wishes he could get back, but 63 on a Sunday at a U.S. Open is absurd," Spieth, who missed the cut after a first-round 78, said in a conference call on Wednesday.
"It's unheard of. It's a fantastic round, and I don't think anybody was surprised, any Tour player was surprised that Tommy Fleetwood did it.
"He certainly has the game, the capabilities, and somebody who has proven he's not afraid of the moment of the shot. I can certainly see him as one of the favourites, somebody who will have a lot of momentum if he works his way up to the lead."
After the brutal test of the U.S. Open where no player finished under par after four rounds, Spieth is expecting no less of a challenge at Carnoustie -- a course that has inflicted its fair share of pain in the past.
"I've seen Opens at Carnoustie. I've seen what the golf course has a reputation and a nickname, 'Car-nasty', among a lot of the players, for being that difficult," the American said.
"Although it won't be necessarily the golf course itself; the conditions can obviously create scores similar to what the U.S. Open just saw. But I thoroughly enjoy links golf.
"I know it will be difficult, but you can obviously expect a little bit of everything in four days over in Scotland."
Three-times major winner Spieth, 24, is yet to win on Tour this year but said he was not concerned with his form heading towards the attempted defense of the Claret Jug.
"Its been an off year. The results haven't been up to my own expectations, and its been putting the majority of the year," he said.
"But I have no doubt in my ability to come back and defend whether form's on, off or anything indifferent. I've proven to myself that I can go from two missed cuts to potentially winning the week after in previous years.
"That's not anything that throws me off. At the same time, it is nice to kind of feel like you're at least proceeding the right way; that you're gaining a little bit of momentum.
"That's what I'm looking for this week, which is important for the defense of The Open."
Spieth is in action at the Travelers Championship this week in Connecticut.
(This story has not been edited by Devdiscourse staff and is auto-generated from a syndicated feed.)