Under Armour is set to become a huge threat to Nike

Under Armour is set for stunning growth over the next decade.

The company is on pace to reach a staggering $20 billion in revenue by 2025, up from nearly $4 billion this year, according to Morgan Stanley analysts.

That's still not as big as Nike, which generated $27 billion in revenue last year.

But analysts say Under Armour is growing at an even fast pace than Nike, as well as Adidas - the two biggest sportswear companies in the world.

By 2030, the Baltimore-based company is expected to become the third biggest global sportswear brand, analysts write. It could even surpass Adidas to take the No. 2 spot.

By that point, Under Armour's market share in North America is expected to jump to 12% from 4% last year, while Adidas' is expected to fall from 5% to 4%, according to Morgan Stanley estimates. Meanwhile, Nike's market share is expected to grow from 21% to 23%.

Two years ago, investors didn't have as much faith in Under Armour's potential for future growth.

But Under Armour proved everyone wrong.

"It was somewhat skeptical UA could capitalize on opportunities to grow in international markets, the footwear category, and the women's category," analysts write. "Since then, UA established it can win in all three areas."

Two-thirds of Under Armour's growth over the next couple decades will come from international sales and the company's digital fitness apps, according to analysts.

The apps, which Under Armour collectively refers to as its Connected Fitness initiative, "create major value," according to analysts.

"We believe UA has already doubled its internet investments' value," analysts write. "These could become worth as much as $20 billion. We view this case as highly credible due to UA's exceptional track record."

In some ways, Under Armour has Nike and Adidas to thank for its rapid growth rate.

The much younger company has looked to its older rivals as a guide for what works and what doesn't as it expands into new international markets.

"This has already helped UA avoid mistakes and probably allow it to continue growing faster," analysts write.