Protect This House

Plank cultivates retailers as intently as he did when he was just starting out. He makes himself available to them by phone or in person, unheard-of access for bigger companies. Under Armour doesn't operate its own stores (as Nike does) or distribute through discounters or department stores (the lone exception is its new line of everyday skivvies), so retailers don't worry about additional competition or a surplus of price-deflating inventory.

But Under Armour also acts big when and where it needs to -- and can sometimes outperform the big guys. Thanks to a state-of-the-art 350,000-square-foot warehouse, it can pack products by SKU, size, and color, and ship to the Sports Authority's 400 stores within days.

The Alpha Underdog

Could Under Armour be the next Nike? Some retailers say yes, but Plank won't bite. The category has room for two brands, he says, and his will be one.

This David and Goliath story isn't over yet. It's too early to celebrate anything. But a tantalizing question lingers: Could Under Armour be the next Nike? A number of retailers think Plank is on the right path, but he won't bite. The category has room for two brands, he says, and Under Armour will be one of them. Even when Nike's "For Warriors" ads were blanketing the airwaves, Under Armour's new $20 shirt was selling out. More important, several months after the Mitts ads hit, women's-apparel sales have increased from 13% of the total to 19%.

The growth curve to becoming a $1 billion company is lined with pitfalls and uncertainty, but don't underestimate Plank. He has a 32-year-old's optimism and ambition and a 50-year-old's levelheadedness about managing a larger organization, the danger of trying to be all things to all people, and his own limitations. "My number-one asset is knowing what I'm good at and what I'm not good at," he says, which is why he surrounds himself with industry veterans. He readily seeks advice from Gap chairman Bob Fisher and eBay CEO Meg Whitman (members of Under Armour's private-equity investor board), and from former Nautica CEO Harvey Sanders.

It also helps to be an inspiring underdog and overachiever, the sort of person who made the Maryland team as a walk-on after the major college scouts snubbed him. Walk-ons rarely play, but at 5-foot-11-inches and 229 pounds, Plank became a starter and eventually a team captain. He has faced bigger, stronger opponents before, like the time he was assigned to block his buddy Ogbogu in practice. The 6-foot-4-inch, 269-pound Ogbogu wound up on his back with a concussion. That, Nike might want to note, is the kind of competitor Plank is.

Chuck Salter is a Fast Company senior writer based in Chicago.