Football fans used to seeing Tom Brady sporting Nike (NYSE: NKE) cleats throughout his career may have noticed the star quarterback had some new footwear during games over the past month. Brady, the New England Patriots' Super Bowl champion quarterback, whose contract ended with Nike this past summer, has been in talks with Under Armour (NYSE: UA) and has been testing out the company's products.  Apparently, they worked quite well for Brady.

On Monday, Under Armour and Brady announced that he will become the company's newest and perhaps highest-profile athlete. However, Brady will become more than just an endorser of Under Armour products. The deal also gives Brady significant equity in the company. Under Armour CEO Kevin Plank said, "Tom is a shareholder in Under Armour. Equity was a part of our deal."

The signing of Brady should bring a huge boost to Under Armour's fledging shoe line. In the past, Under Armour has focused on signing players from the defensive side of the ball to represent its brand. However, the company has shifted its focus this year to signing more flashy offensive players who put points on the board and excite fans. The company's other most recent signings were wide receivers Anquan Boldin and Miles Austin.

While Under Armour has many extremely successful athletes on its roster, perhaps only swimmer Michael Phelps can compete with Brady on a popularity level. Brady has also become a fixture in tabloid magazines due in part to his marriage to supermodel Gisele Bundchen and previous relationship with actress Bridget Moynahan. Brady's appeal beyond football will help create an even larger platform for the relatively new brand worldwide.

Brady also has large sponsorship deals with Comcast (Nasdaq: CMCSA), Movado Watches, and Smartwater by Coca-Cola (NYSE: KO).

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Andrew Bond owns no shares in the companies listed. Nike is a Motley Fool Stock Advisor recommendation. Under Armour is a Motley Fool Rule Breakers selection. Under Armour is a Motley Fool Hidden Gems recommendation. Coca-Cola is a Motley Fool Inside Value pick. Coca-Cola is a Motley Fool Income Investor selection. The Fool owns shares of Under Armour, Nike, and Coca-Cola Try any of our Foolish newsletters today, free for 30 days. The Fool has a disclosure policy.