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The Baltimore-based company has been scoring a number of key endorsements lately, including golfer Jordan Spieth.
Now, it's going after one of the biggest stars in basketball - Oklahoma City Thunder forward Kevin Durant.
Under Armour is reportedly offering Durant - who has long been loyal to Nike - a package worth as much as $285 million over 10 years.
It would be Under Armour's biggest endorsement deal, representing about 10% of its annual marketing budget, according to ESPN.
The record-setting deal is intended to widen Under Armour's share of the basketball market, which now stands at less than 1%. By comparison, Nike is estimated to control 96% of the market.
"[Durant's] one of the premier basketball players in the country," Matt Powell, a
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Wall Street is betting on Under Armour's ability to chip away at Nike's empire. The stock is up more than 1,000% over the past five years.
But it's still considered a clear underdog. Under Armour has a market cap of just $15 billion compared to more than $68 billion for Nike.
The company has experienced massive growth over the last two decades, but it's sales are still only a tiny fraction of Nike's.
When Under Armour was founded in 1996, it had $17,000 in revenue. This year, it's expected to bring in $3 billion. By comparison, Nike is expected to bring in $28 billion this year.
BusinessInsider.com