Retail: Game, set and matching outfit for Djokovic

As Nike erects giant posters on Warsaw tower blocks in advance of today's Euro 2012 kick-off and Adidas spreads its stripes around the tournament and the London Olympics, the two giants are in the middle of their annual summer heavyweight battle to sell the most replica shirts, footballs and trainers.

As in football and the Olympics, the biggest stars in tennis are generally clad in gear from the big two. Both Rafa Nadal and Roger Federer are tied to Nike and Andy Murray famously dumped Fred Perry for Adidas in 2009. From Agassi to Sampras via the Williams sisters and Maria Sharapova – tennis's big stars generally Just Do It.

Which is why the pre-French Open announcement that Novak Djokovic – the world's No 1 men's player – was signing a lucrative five-year clothing deal with Uniqlo, the Japanese casualwear store known for its stylish Oxford shirts and plain separates, seemed so odd. Wearing the shop's red, square logo, Djokovic has made his way to the semi-finals at Roland Garros, where he meets Roger Federer today.

Is this Uniqlo taking a swing into the sportswear market – worth some £4.5bn in the UK alone in 2011 – or merely a way to promote its casualwear? It's certainly an interesting deal; Djokovic's role as a (sigh) "global brand ambassador" will see him wearing custom-made Uniqlo clothes on and off the court – a bit like Adidas making Lionel Messi suits to wear to dinner. But where Nike can sell Cristiano Ronaldo's boots and Barcelona's kits, Uniqlo isn't selling Djokovic attire (though it does have some similar dry-mesh garments).

So, if the brand's not in it to sell sportswear, what's the investment in a tennis superstar worth for Uniqlo? "It's all part of a general movement in the fashion sector – especially in the retail sector – into sportswear," Isabel Cavill, an industry analyst for Planet Retail, says. She points to the rise of Gap's Athleta brand, popular Canadian yoga label Lululemon and H&M's pop-up Olympic sportswear shop as evidence.

But Uniqlo's tie-up with Djokovic – on a the back of similar deals with two Japanese players – is definitely the biggest. "It's quite a big thing for Uniqlo," she says. "It has had a problem with getting its brand seen. It has a strategy of opening up big flagship emporiums on major shopping streets, but it hasn't opened stores on smaller UK high streets to establish a brand presence. A lot of people still don't think of Uniqlo as the place to go to buy basics. But teaming up with such a major sportsperson will do it a lot of good."

Uniqlo isn't the only unlikely brand to pin itself on a superstar sporting name recently. US lacrosse and hockey firm Warrior has just started a £25m-a-year sponsorship of one of football's most famous names – Liverpool. The New Balance subsidiary will be hoping Liverpool's fame will bring spring it into non-US football-watching markets. A similar effect to Uniqlo on American and European high streets.

But there are few precursors to a non-sporty clothing brand such as Uniqlo signing up a big name. Perhaps the only comparison is Benetton's ownership of a successful Formula 1 team in the early Nineties. Since then, though, Benetton has been through a steady period of decline. Whether Uniqlo's gambit will be an ace or a fault might depend on Djokovic's form over the next five years, but on the eve of his 15th grand slam final, I popped into a Uniqlo store to ask about his kit and was met with a bemused look. High-street fashion and pro sport might make a nice set, but it remains to be seen if it proves a good match.