Rumors swirled Wednesday night that Nike was considering acquiring rival Under Armour for $100 a share, according to the London Times.

Under Armour's stock shot up more than 7 percent in post-market trading behind the rumors, but later dropped 1.6 percent in Thursday's trading when a Nike spokesman denied the rumors.

Longbrow Research senior analyst Jonathon Grassi says that the rumors of Nike acquiring Under Armour have been going around for years and that he doesn't think Under Armour is ready to sell just yet.

I don't think (CEO) Kevin Plank is interested in selling the company right now, Grassi told the IBTimes. He owns 75 percent of the voting shares and isn't looking to sell.

Even though Nike, not Under Armour, is the one that denied the rumors , Grassi actually thinks Nike is much more interested in buying than Under Armour is interested in selling.

Nike is more than 10 times the size of Under Armour, in terms of market cap, but faces stiff competition from the company in the United States. Nike owns the footwear market and Under Armour dominates the athletic apparel market, though both have tried to enter into the other company's primary market.

Under Armour has been more aggressive of late in the footwear market, launching new football and basketball shoes as well as signing high profile athletes. The biggest was NFL star Tom Brady, but the company has also landed recent NBA players Brandon Jennings, Derrick Williams, and Kemba Walker.

I think Nike would like to acquire them because Under Armour is one of their biggest competitors in their domestic market, Grassi said. From Nike's perspective, it makes sense.

But Grassi doesn't think that now is the right time for Plank and investors to sell the company to Nike.

From Under Armour's perspective it doesn't make much sense right now because there is so much upside to the company.

Under Armour's sales primarily deride from the United States and have only just beginning exploring all of the different international opportunities. Investors love a company poised to grow and Under Armour is set to do just that when it expands more internationally.

Expect More Flashy Fashion from UA

The sports and media worlds buzzed recently over Under Armour's Maryland football uniforms. The Maryland Pride uniforms paid homage to Maryland's state flag and dominated social media for days after they were unveiled in a Labor Day primetime game against Miami.

Even two weeks later, The Washington Post and The New York Times had cover stories on the changing nature of college football in regards to uniforms and prominently mentioned Maryland and Under Armour in both.

Those ballsy uniforms netted Under Armour millions of dollars of free advertising and are a strategy that Grassi sees the company utilizing more going forward.

I think you will continue to see them push on performance and add some fashion aspect, he said. First and foremost Under Armour wants to be a performance brand, but needs to raise the stakes on the fashion brand.

The talked about uniforms is a play straight out of Nike's playbook. Nike CEO Phil Knight has decorated his alma mater, Oregon, with some of the flashiest, most outrageous uniforms in all of football. The uniforms typically get criticized by media, but a recent story in ESPN offshoot Web site Grantland indicated the crazy uniforms are having a positive effect on Oregon's football program.