It was the kind of bag you might see in the overhead compartment of an airplane’s first-class cabin. Except he was carried onto center court at Wimbledon by a 6ft2in redhead.

Jannik Sinner, 21, the eighth-ranked Italian Tennis player in the world, broke with tradition on Monday when he appeared on court with a bespoke sports bag wrapped in Gucci’s “GG” monogram, red suspenders and green slung over one shoulder.

For the average sports fan, that might not sound so extraordinary. In basketball, walks through the tunnels have become mini fashion shows as players head to their locker rooms soaked in designer clothes and accessories.

But that kind of sartorial energy has yet to come to tennis – especially not Wimbledon, the most traditional of the four Grand Slam Tournaments, with its stringent all-white uniform requirements. (This is the first year that women playing at Wimbledon have been allowed to wear non-white underwear, to ease period anxiety.)

Players at Grand Slam tournaments abide by a rule book that regulates what they can wear and carry on the courts. There are limits on the size, placement, and number of logos on their sleeves, collars, headbands, socks, and yes, gear bags.

Many players carry both a racquet bag and a personal duffel bag on the court, but these are usually the obvious duffel bags. Hours before the start of Mr. Sinner’s match, for example, Novak Djokovic (ranked second in the world) entered center court with two white bags made by Head, his racquet sponsor.

Mr Sinner’s appearance with his sports bag was the first time, Gucci said, that a tennis player had been allowed to carry a luxury logo bag on court. Even beloved players in the fashion world, like Roger Federer and Serena Williams, who had a close relationship with Gucci, hadn’t done so until their retirement. For Ms Williams’ final game last year, she carried a Wilson racquet bag and duffel bag stamped with her own Nike monogram logo.

Mr Sinner, whose initials also appear on his Gucci bag, was named the brand’s ambassador last July. Gucci said it worked with Mr Sinner’s team to secure approvals from the International Tennis Federation, Association of Tennis Professionals and Grand Slam tournaments, including Wimbledon, to ensure the bag met the necessary requirements. He carried his racquets in a standard white Head bag.

Gucci isn’t the only luxury house looking to align itself with young tennis stars. Naomi Osaka and Carlos Alcaraz were ambassadors for Louis Vuitton. Mr. Alcaraz, 20, who is ranked No. 1 in the world, was announced as Vuitton ambassador on June 28, just five days before the start of Wimbledon. On the same day, Gucci hosted a chic private dinner for Mr Sinner in London to celebrate his third year at Wimbledon.

Mr. Sinner and Mr. Alcaraz are budding rivals among the next generation of male tennis stars. At last year’s US Open, they played a quarter-final match that lasted over five hours and ended before 3 a.m. – the last ever US Open match.

Unlike Mr. Alcaraz, Mr. Sinner does not have a Grand Slam title, although tennis tipsters are hopeful. The Italian has one thing the Spaniard doesn’t: a group of fervent fans, called the Carota Boys, who dress up in carrot suits and travel to tournaments to support him.

Mr Sinner doesn’t seem to consider the bag, which has been made from a canvas material with leather trim, a serious break from tradition. In an email, he wrote that he was very fond of the traditions, including the Wimbledon dress code. For the design of the bag, he and Gucci wanted “something that could have been taken from the Gucci archives”.

The straps are removable and the interior contains hidden water bottle pockets. He said he would use it to carry a change of clothes, nutritional supplements, sunscreen and anything else he might need for a few hours in the field.

When asked if he had made any specific requests of Gucci, Mr Sinner wrote: “I wanted the bag to be comfortable to carry and have enough to keep all my stuff inside. My priority was functionality, I guess.