Under Armour's early bet on Masters champ Spieth pays off

Jordan Spieth in the green

Jordan Spieth's incredible Masters victory on Sunday not only resoundingly announced the arrival of golf's newest young gun, it also highlighted the bitter rivalry of two of the world's biggest sports apparel makers, Under Armour and Nike.

Throughout the four-day tournament at the storied Augusta National Golf Club in Georgia, the 21-year-old Spieth was clad head to toe in logos for Under Armour, which had originally signed him in 2013. In January, he agreed to a 10-year sponsorship contract extension.

Spieth said on Tuesday he's very happy with Under Armour and his other sponsors. "This is what they expect of me. It's not like this [Masters win] should really change much. They took a chance. They've put their investment in to me to be wearing this jacket," referring to the iconic green jacket given to Masters champions in addition to the prize money, which was $1.8 million to the winner this year. (Tweet This)

"It's not like this is a different level than they want to see," he told "Squawk Box" in an interview. "I feel like I'm doing what I'm supposed to do for them."

Jordan Spieth watches his tee shot on the seventh hole during the final round of the 2015 Masters Tournament at Augusta National Golf Club on April 12, 2015, in Augusta, Georgia.
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In a sport dominated by Nike's big stars, such as Tiger Woods and Rory McIlroy, Under Armour, like Spieth, is a relative newcomer. Woods has been recently struggling with injuries, though he did show promise at the Masters in his return to competitive golf. But McIlroy, ranked No. 1 in the world, has been on fire.

"This is a transformational moment for the game and for our brand," Under Armour wrote in a statement emailed to CNBC. "Much like Under Armour, Jordan is just getting started, and he is changing the game every time he tees off." Nike was unavailable to respond to CNBC's request to comment.

With his Masters win and tour victories in the lead-up to Augusta, the Dallas-born Spieth has vaulted up to No. 2 in the world. But he remains humble. "Rory is obviously much more accomplished than I am. He is older. He's got four majors and numerous wins. I don't consider myself on that level yet. But I think I took a giant step forward a couple days ago."

Spieth's wire-to-wire Masters win was his first major golf tournament victory. In doing so, he became the second youngest Masters champion ever behind Woods. And of the numerous records broken by the Texan at Augusta, Spieth tied the 18-under Masters record set by Woods in his first major tournament victory in 1997.