Back in March, I told you Under Armour (UA) had huge upside potential.

The stock was already a big winner for investors. Since going public 10 years ago, UA surged more than 1,100%. And when I told you to buy shares, the stock was trading near an all-time high.

Since my call, UA is up 34%. That compares with the S&P 500 index, which is up 1% over the same timeframe.

Despite the recent outperformance, UA still has much more upside potential. In fact, the stock is likely to outperform the markets over the next several years.

Let me explain …

In mid-July, UA reported strong second-quarter earnings. The company grew its sales by 29% year-over-year. This was the eighth-straight quarter of 25%-plus revenue growth for the company. UA also raised its full year sales and earnings guidance.

These are exceptional numbers considering most companies today are struggling to grow sales and earnings in the low-single-digits. UA also kept its gross margins close to 50% as the company continues to grow its brand.

But when you take a closer look under the hood, the numbers were even more impressive.

You see, UA’s goal is to become the largest sports apparel company in the world. Over the past few years, they surpassed Adidas (ADDYY) to become the second-largest sports apparel company in the U.S. (based on revenue).

But UA still lags industry leader Nike (NKE) by a wide margin.

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For example, UA generated $3.4 billion in sales over the past 12 months. This compares to Nike, which generated $30 billion in sales over the same timeframe. In short, Nike is almost 10 times the size of UA when it comes to sales.

Nike’s bread and butter is athletic footwear. The company commands more than a 60% market share in America. Its closest competitor only has a 5% market share in athletic footwear.

In total, Nike generates roughly $18 billion a year in global footwear sales. To put this in perspective, UA generated less than $500 million in footwear sales over the past 12 months.

However, UA is making a major push into this segment. In fact, athletic footwear sales increased by 40% last quarter. This segment now makes up roughly 20% of UA’s total revenue.

Strong demand in this segment was mostly due to huge sales of Stephen Curry’s “Curry One” basketball sneakers. Curry was named the most valuable player in the NBA this past year and considered one of the greatest shooters to ever play basketball. His Golden State Warriors also won the NBA championship.

Curry is now the face of UA’s footwear segment. And he is touring Asia next month with the company. Curry will visit Tokyo, the Philippines, Beijing, Chongqing and Shanghai. I’m sure this will help increase footwear sales internationally — which is another massive growth opportunity for UA.

UA generates 11% of its sales from overseas. This amounts to roughly $400 million. In comparison, Nike generates roughly 53% of its sales overseas. This amounts to roughly $16 billion in sales.

However, UA is growing international sales by almost 100% year-over-year. The company is making a major push into Latin America, Europe and Asia. They plan to open at least 100 new stores overseas. Plus the company has opened 17 regional offices outside the U.S.

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Its recent partnership with superstar Jordan Spieth also bodes well for its international growth plans.

Spieth is just 22 years old and ranked the No. 1 golfer in the world. He’s already being compared to legends Tiger Woods and Jack Nicklaus. His popularity is off the charts right now. Television ratings are through the roof every time Spieth’s name is on the leaderboards.

Golf is one of the most widely followed sports around the world — especially in Europe. He will be promoting UA for at least 10 years based on his new contract with the company. I’m sure Spieth will follow in Curry’s footsteps — touring international markets with UA to expand the company’s brand.

Despite these positives, the one drawback for investors is valuation.

UA trades at 70 times forward earnings and 15 times book value. That’s super-expensive compared to the average company in the S&P 500, which trades at 17 times earnings and less than three times book value

But these numbers are more of a smokescreen. In other words, investors scared by this high valuation need to look at the massive growth potential that lies ahead for UA.

For example, research firm Trefis expects the global athletic apparel market to grow to $178 billion by 2019. To put this number in perspective, UA is one of the fastest-growing companies in the industry. They now rank No. 2 in total sales in the U.S.

Yet, UA is only capturing less than 2% of the entire athletic apparel space right now.

As I explained above, the company is seeing massive growth in athletic footwear and international sales. These are multibillion-dollar markets that Nike has dominated for decades.

If UA can grow its total market share to just 5%, the company would grow its sales by more than threefold!

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I am also placing zero value on UA’s digital fitness social media platform. The company has more than 140 million people on its fitness app platform. These are people who use “connected” devices (wearables) to track their workouts.

It’s by far, the world’s largest fitness platform with over 100,000 people signing up daily. Over 1 billion workouts and over 5 billion different types of food have already been logged. Some experts believe UA’s fitness platform will be a multibillion-dollar business.

UA is still firing on all cylinders. The company locked up two of the most popular athletes in the world (Curry and Spieth) to long-term contracts. They will be huge promoters of UA at least over the next decade.

Plus, the company’s plan to grow footwear and international sales is working. That’s why the stock surged last month after UA reported earnings.

UA still has enormous growth potential. The stock is trading at a lofty valuation. However, it’s a similar valuation to where Apple (AAPL), Celgene (CELG) and Netflix (NFLX) were trading 10 years ago — during their early growth days.

Today, these industry leading companies are up an average of 2,500%! Investors who bought these stocks 10 years ago are probably sitting on a small fortune.

If UA continues to grow its brand internationally and become a dominant player in athletic footwear, investors are likely to see huge gains in the stock 10 years from now.