When the top two male players take to the court at Flushing Meadow this week, the look they sport will be as different as their games. Roger Federer, the number-one seed, embodies classic tennis in both the sartorial and athletic senses. Rafael Nadal, the 20-year-old Spanish sensation, represents the sport’s transformation from a game of finesse to one of brute force, and its style from classy to what many tennis and fashion insiders consider crude.

The champions’ diverging clothing preferences are more than symbolic of the sport’s democratization, not only in terms of who plays and follows tennis but also what one wears to play. It’s about the encroachment into tennis of street fashion, and the supersizing and vulgarizing of everything from food to handbags to wedding celebrations.

Once considered the most elegant of athletic endeavors, tennis until recently had a lily-white dress code in which personal style was largely telegraphed through subtle tweaks — Rene LaCoste’s polo shirt, John McEnroe’s untucked shirttail, Patrick Rafter’s samurai hairstyle. Players usually looked like they were part of a team, even if it could only have a loose-affiliation type name like “Team Tennis.”

“Fashion in sport traditionally put the sport ahead of the individual,” Glenn O’Brien, the writer who pens the “Style Guy” column for GQ magazine, said. “Not anymore, and definitely not in tennis. It’s akin to the Yankees playing in their own clothes instead of pinstripes.”

Mr. Nadal is the most visible of the flagrant violators of classic tennis fashion who so irks purists and style hounds. It’s not the warrior-cum-skate rat shoulder-length hair held back by a sweatband, for the look has precedent with some of the sport’s style (and overall) greats, namely Bjorn Borg. Even the clean-cut Federer started his career with a ponytail. (Andre Agassi’s early-era mane may have achieved icon status but never respectability, what with its teased and frosted high-maintenance obviousness.)

Nor is it necessarily the calf-length clam diggers Nadal prefers to shorts. Mr. O’Brien points out that their length and bagginess aren’t too far off of the sport’s modern roots at the turn of the last century, when men wore full-length trousers whether playing tennis or simply wearing the casual sportswear of the time.

It’s the muscle shirt that makes fashionable men wince. “I wonder if he has any discretion,” the executive editor of the fashion Web site men.style.com, Tyler Thoreson, said. “That tight sleeveless top is all about showing off that completely ripped upper body.”

Of course it’s also about being a 20-year-old testing the limits of appropriate dress, not to mention intimidating one’s opponent. But Mr. McEnroe and Jimmy Connors, the ultimate bad boys of tennis, managed to push all kinds of buttons and intimidate the heck out of their opponents wearing outfits similar to everybody else on the tour. They politely covered up their trim physiques with a white collar shirt.

There is some hope that a classic look — albeit an updated version of it — could make a comeback.

“If Ralph Lauren managed to get players into his clothes, we might see the return of what is considered a more traditional tennis uniform,” Mr. O’Brien said.

Mr. Lauren has already dipped his toes into the tennis waters, so to speak, designing this year’s Wimbledon uniforms for umpires and ball boys and girls to some acclaim (although anything would have been an improvement over the old ill-fitting green and purple numbers).

Thanks to fashion’s recent preppy turn, collar shirts are replacing Tshirts on more players. Andy Roddick, who has a new sponsorship contract with Lacoste, is the most visible player to embrace a more classic look. But don’t look to Mr. Roddick for the bodyconscious styles that dominated pro tennis in the ’60s, ’70s, and ’80s.

“Andy wears tennis wear more like street wear. He likes it less tight, more baggy,” the vice president of marketing for Lacoste, Tamara Rosenthal, said.

Of course, the baggy look — especially on bottom — has dominated pro sportswear since Michael Jordan reigned over the NBA in the early 1990s. But tennis has always had style rebels striving to differentiate themselves from the pack. Perhaps the most rebellious, attention-getting look the next tennis style upstart could adopt is the buttock-skimming short shorts worn by Messrs. Connors, McEnroe, Borg, and just about every other player from that great era. Players on the women’s tour certainly have.