CEO Kevin Plank says Under Armour still has eyes on being No. 1 despite stock slide

Under Armour CEO Kevin Plank said his company still has plenty of room to grow, despite concerns about the company's slowing sales.

"We have eyes on number one. We are one of the top three brands in the world and, more importantly, we have eyes on being the number one brand in the world, and that's the kind of company you're investing in," Plank said in an interview with CNBC's Scott Wapner on "Halftime Report" on Wednesday.

On Tuesday, Under Armour's Class A shares saw their worst daily performance since Nov. 12, 2008, amid concerns that the company is losing steam, especially in its biggest market, North America. The stock continued to slide more than 2 percent on Wednesday, following downgrades at a number of research firms.

The athletic apparel company saw third-quarter sales of $1.47 billion, above analyst expectations for $1.45 billion, according to a Thomson Reuters consensus estimate. While that figure was up 22 percent from the year-ago period, it was Under Armour's slowest sales growth rate since the third quarter of 2010.

But Plank said Under Armour is the "kind of company that fights back" and pointed to the company's record of double-digit sales growth. On Tuesday, Under Armour posted its 26th-straight quarter of revenue growth of 20 percent or more.

"I don't know of any other pace than for us to move fast. It's all we've done," Plank said.

Plank, who founded Under Armour in 1996, said that he thinks his company is "writing the book" on being a "growth juggernaut."

"We're in the arena. There is blood and sweat on our face ... we pull rabbits out of our hats for a living," Plank said.