Even in pingpong.
"We would play until he won," Kuehl said. "I've been around great Hall of Fame football players who loved to compete. Jordan is one of those guys."
Over intense games of table tennis and cards, the two forged a bond that's paying off spectacularly for Under Armour. In January 2013, the Baltimore-based sports apparel brand signed Spieth, then 19 years old and a two-time U.S. Junior Amateur champion, to an endorsement deal. But the inspired move came this January when Under Armour, at Kuehl's urging, tore up the original four-year deal and locked in Spieth to a 10-year contract.
Spieth went on several months later to become just the sixth golfer to win the Masters and U.S. Open in the same year, and now aims to capture the single-season Grand Slam by winning the British Open in July and the PGA Championship in August, a feat no golfer has achieved since the Masters began in 1934.
Spieth's courtship by Under Armour provides a high-profile example of how the company scouts potential endorsers, often targeting young up-and-comers, and how it pays off. Since signing Spieth to wear Under Armour from head to toe, the brand has more than doubled its golf-related earnings.
"Before the Masters, only 19 percent of consumers knew who he was," said Mary O'Connor, a senior vice president at The Marketing Arm in Dallas, citing the agency's Celebrity DBI, an index that measures public awareness and impressions of endorsers. "After the Masters, that jumped to 35."
Under Armour "will hit the gold mine if Jordan manages to win the Grand Slam," she said. "The marketing value of his success can't be determined yet. It's too soon."
Spieth wears Under Armour caps, shirts, belts, pants and shoes, which he helped develop and test, and which were sold to the public beginning this spring. TV viewers cannot watch Spieth play without catching sight of the UA logo. Spieth's outfits for every day of the British Open, which begins July 16, will be scripted in advance.
On his desk at Under Armour's headquarters, Kuehl, the company's vice president for sports marketing and sponsorships, has a copy of a report calculating the value of Spieth's Under Armour logos appearing during the Masters telecast. Optimum Sports, a marketing and media agency, calculates that Under Armour received about $7 million worth of media exposure in last year's Masters broadcast when Spieth tied for runner-up and about $21 million this year when he won.
Spieth also endorses AT&T, Titleist and Rolex.
"Jordan has four partners. He's not cluttered," O'Connor said. "You see Under Armour on his body. You see AT&T on his bag. You see Titleist in the bag. And you see a Rolex on his wrist. And that is it. There is no other part of his body that can be endorsed."
Under Armour's scouting of potential signees includes meticulous assessments of character and drive, as well as skill.
"For me," Kuehl said, "I try to really get into their head and their heart to see if I can figure out: Are they motivated by money? Are they motivated by fame? What's their work ethic like? What's the family like? What's pulling them? What can be a distraction to them? Do they need help getting focused? Do they love to compete?"
Kuehl, 43, learned scouting from actual scouts. When he was in the NFL, he would occasionally chat up scouts on the sidelines during football training camps and practices.
"I picked their brain on 'What are you looking at? What do you see?'" he said.
Spieth's father, Shawn, was a baseball player at Lehigh University and his mother, Chris, played basketball at Moravian College. As a top-ranked junior, Spieth not only hungered to win, "he was used to having people go after him, being the target," Kuehl said.
Kuehl began tracking Spieth when the native Texan was a 16-year-old amateur in contention at the 2010 Byron Nelson Championship, in which he tied for 16th. Kuehl remembers thinking: "If he gets good enough, he'll be very comfortable when he shows up at a tournament having the extra attention, the extra media, the extra eyeballs and players going, 'I want to beat him.'"
Kuehl's relationship with Spieth was aided by his own competitiveness. It gave the two common ground. Undrafted but signed by the San Francisco 49ers as a free agent in 1995, Kuehl cobbled together an unlikely 12-year, four-team NFL career, including five as a defensive lineman and seven as a long snapper.
He understands golf but leaves it to others to break down the mechanics. Spieth's swing is considered unorthodox because he bends his left arm at the top of his swing.
"I'm like a six or seven handicap," said Kuehl, who is from Montgomery County. "But with me, it's about relating to the athlete. I think professional athletes, although they have different skills, have similar mindsets."
Under Armour, which has signed about a dozen golfers, is still a relatively new and small player in the sport.
But some see an appealing novelty in Under Armour's brand. Spieth, who was unavailable for comment last week, has said previously that he relates to the company's underdog image.
"Under Armour is new, aggressive, slick, classic but athletic — kind of how I always wanted to be perceived," Spieth told Forbes magazine in 2013 after first signing.
Hunter Mahan, the first golfer signed by Under Armour (in 2003), considered it "a really unique opportunity to get involved at the ground floor," said Chris Armstrong, his agent.
"I definitely do think the Under Armour brand has been a differentiator for Hunter. It's been a source of great interest for fans," Armstrong said. "They're a brand that is not traditional to golf, so people want to understand what's coming, how they're being innovative and pushing the envelope."
Spieth's success has amplified that interest.
"The one thing you can't predict is performance," Armstrong said, "but they've certainly done a good job of researching and placing their bets on the right people."
Top Under Armour partners in other sports include New England Patriots quarterback Tom Brady; Golden State Warriors guard Stephen Curry, the National Basketball Association's MVP; and Washington Nationals' outfielder Bryce Harper. While Brady was a known quantity when he signed with Under Armour, both Curry and Harper were new professionals just beginning to make a mark on their sports.
Under Armour topped $3 billion in revenue for the first time last year — a little more than one-tenth of archrival Nike's figure.
To compete with Nike, Under Armour has often targeted "up-and-comers rather than established winners, as evidenced by Nike signing Rory McIlroy, while Under Armour doubled down on Spieth," said Jonathan Jensen, a sports marketing consultant and assistant professor in the Girard School of Business at Merrimack College in Andover, Mass.
With less room for error, "you have to figure that Under Armour does place more importance on an athlete's off-field profile and the potential for issues. They just cannot take the same chances as Nike can," said Jensen, who has negotiated athlete endorsement agreements for brands such as Microsoft, McDonald's and Amway.
Kuehl, who also oversees Under Armour's football and lacrosse sponsorships and college outfitting deals, said he once misjudged an athlete the company partnered with.
"I made one mistake here — and I'm not going to get into it — signing an athlete," he said, declining to name the endorser. "I took a reach. I thought I could mold somebody. It didn't work out. And that was the last time."
There were no reservations about Spieth.
Midway through the golfer's initial deal, Kuehl said he presented CEO Kevin Plank with options for retaining Spieth, who was starting to have enough success to attract the interest of Under Armour's rivals.
Kuehl recalled saying: "Let's wait it out and let all these companies start feeding him little bits and pieces of what they can do for him? Do we really want to compete with that, Kev?"
The announcement of the new contract came in late January.
"We knew what we had," Kuehl said.