They go back more than a decade. Now both 24, they first competed against each other at the age of 13 in a junior all-star event in Texas. Spieth won by five strokes.
At 14, they were teammates on a U.S. junior team that competed in France.
In college, Spieth (Texas) took out Thomas (Alabama) on the way to a Longhorns championship.
More recently, at the playoff event two weeks ago in Boston, the two of them were tied with five holes to play. Thomas birdied 15 and then left Spieth behind by three shots.
Their annual vacation to the Bahamas in late spring with a group of young pros has become a Twitter staple.
There were some signs Thursday they may be growing just a bit weary of the whole besties story that is sure to follow them for the duration.
Asked if they had struck any kind of pact in advance of this tournament to go low and remain paired together throughout the four rounds, neither really seized on that half-serious suggestion.
"Yeah, that would be nice. We certainly would both enjoy that for sure," Spieth said flatly.
"As long as it's late," Thomas said, meaning he'd be among the leaders, "I don't care who I'm playing with."
"We're both doing our own thing out there," Thomas added. "We're not out there to entertain each other. So, it's just a nice bonus sometimes between shots, but that's about it."
Why, at this pace, they'll be positively sick of each other by Sunday.
(c)2017 The Atlanta Journal-Constitution (Atlanta, Ga.)
Visit The Atlanta Journal-Constitution (Atlanta, Ga.) at www.ajc.com
Distributed by Tribune Content Agency, LLC.