Spieth moves more than the needle. He moves product.

The Under Armour Sweaterfleece he wore during this year’s Open Championship in July was already sold out by Monday of that week -- typical of most, if not all, of his apparel during a major championship.

Since signing him in January 2013, the company’s golf revenue will have more than tripled by the end of this year. In North America, its apparel ranks behind only Nike.

On a more granular level, the growth has been even more explosive. Under Armour belts -- a product that gets most of its exposure in golf -- have seen sales figures grow more than sevenfold from just two years ago, according to one industry insider, while its numbers in the accessories market have almost quadrupled the past year.

Not bad for a company that as a whole has only been in existence since 1996 and didn’t ink its first golfer (Hunter Mahan) until 2004.

Its real eureka moment in golf, however, came in April when Spieth romped to a wire-to-wire victory at the Masters.

Founder and CEO Kevin Plank told ESPN.com that his company “grew up today. He was challenged by the greatest players in the world on the biggest stage, looked them straight in the eye and never blinked.”

“He’s validated us,” adds Kuehl. “From a brand perspective, people started looking at us differently. This was a new place for us. We’d always been a team sport brand.”

Even before Spieth, Under Armour had interest in golf. How it got involved is a story much in line with how it was founded to begin with: One of opportunity.

Plank’s first big deal was getting his alma mater’s football team to use his gear at the University of Maryland. Not long after, an official called Under Armour and said the school needed polo shirts because that’s what coaches liked to wear during games.

The company quickly made a batch in team colors and sent them over.

The following summer, the phone rang again. They needed more shirts because much of the staff was playing golf in them.

The light bulb went on.

Eventually, Under Armour signed Mahan. They wanted a young player, and Mahan was 22 at the time and playing his first full season on TOUR. Mahan, who lives in Dallas, was represented by Jay Danzi.

Danzi became Spieth’s agent when the golfer turned pro. Having had that previous business relationship with Mahan, it was a natural connection for Under Armour to be interested in Spieth.

When Danzi told Under Armour that his young client had an interest in representing their apparel, the company laid out a plan in an attempt to sign him and brought Spieth to the global offices in Baltimore.

Spieth called it a recruiting trip. What sold him was an emerging golf brand that was athletic in nature. It was also familiar to him: Spieth knew about Under Armour from other sports he played growing up, including baseball.

“I went up there and when I left Baltimore, it was a no-brainer,” he told USA Today. “I was going with them. I see where they were going in golf. The whole atmosphere there, seeing the headquarters, I loved the attitude there. It kind of reflected my own attitude.

“I was in the underdog role. I looked at myself as the underdog. I still do ... Under Armour, that’s kind of been their grit, being the underdog, finding out-of-the-box ways to innovate, to get things done. And their growth in golf is going to be phenomenal. They showed so much trust in me.”

In January of this year, they showed even more. Under Armour signed Spieth to a 10-year deal.