Roger Federer: The greatest sportsman ever?

Switzerland's Roger Federer holds his trophy after defeating Spain's Rafael Nadal during the men's singles final at the Australian Open tennis. Photo / AP.

Darren Walton has covered Roger Federer's unparalleled tennis career since the Swiss's teary loss to Arnaud Di Pasquale in the bronze medal match at the 2000 Sydney Olympics.

He believes the 35-year-old deserves to be considered as possibly the greatest sportsman ever. Sure to spark debate, here are his top dozen contenders (in alphabetical order):

MUHAMMAD ALI: The global icon transcended boxing as much for his polarising personality and political and morals stands as for his charisma and class inside the ring. Heavyweight champion in 1964, 1974 and 1978, Ali was ranked the greatest athlete of the 20th century by Sports Illustrated and Sports Personality of the Century by the BBC.

USAIN BOLT: Never has a sportsman been more aptly nicknamed than the Lightning Bolt. His haul of back-to-back-to-back golds in the Olympic 100m and 200m and two 4x100m titles will surely never be equalled. Bolt's world records of 9.58 seconds in the 100m and 19.19 in the 200m are in another stratosphere. The only world title he has missed out on since 2009 came when he false-started in the 100m final in 2011. In a sport which often struggles for mainstream traction outside the major championships, the charismatic Jamaican is a Godsend.

DON BRADMAN: So many of the Don's achievements will almost certainly never be equalled, most notably his iconic Test batting average of 99.94. The boy from Bowral is widely recognised as cricket's greatest, having scored runs with remarkable consistency and elegance in a 52-Test career. Knighted in 1949, voted the greatest male athlete of the past 200 years by the Australian Confederation of Sport in 1988 and one of Australia's true national treasures.

ROGER FEDERER: The stylish Swiss defied Father Time to match Jack Nicklaus's magical mark of 18 golf majors at an age when most tennis players are long retired and while his peers are at the peak of their own physical powers. Ending a decade-long grand slam run of outs against his greatest rival, Rafael Nadal, in the Australian Open final to do it - in the 35-year-old's first official tournament back after a six-month layoff - added the exclamation to an incomparable career.

MICHAEL JORDAN: For the better part of two decades, untold millions of basketball fans wanted nothing more than to Be Like Mike. He was awarded the finals MVP for each of the Chicago Bulls' six titles from 1991-93 and 1996-98. Five times he was voted the NBA's player. His second Olympic gold came as a member of the original and greatest Dream Team in Barcelona in 1992 - where he was clearly the biggest star in the basketball galaxy. Air Jordan sneakers are best sellers to this day. And the likes of Shane Warne, Michael Clarke and David Beckham chose to wear No.23 mostly because they too wanted to Be Like Mike.

JAHANGIR KHAN: If not the greatest, the Pakistani squash legend was unquestionably the most dominant in one of sport's most demanding individual pursuits. Boasting extraordinary racquet skills and stamina, he went unbeaten for 555 matches and won the British Open - the Wimbledon of squash - 10 years in a row.

ROD LAVER: Federer's idol is the only man ever to complete two calendar-year grand slam sweeps, winning the Australian, French and US championships, plus Wimbledon, as an amateur in 1962 before emulating the fabled feat as a professional in 1969. With a forearm as big as Popeye's, the left-hander's mix of baseline power and elegance and touch at net separated him from his rivals in one of tennis's most competitive generations.

JACK NICKLAUS: The Golden Bear's unforgettable 1986 Masters triumph - featuring a back-nine six-under-par 30 to deny Greg Norman - at age 46 and 24 years after netting his maiden major remains one of sport's greatest fairytales. Tiger Woods, who also belongs in this conversation, has spent his entire career obsessing over catching Nicklaus, yet for all his accomplishments, is still four majors short with the clock ticking.

JESSE OWENS: The son of a share-cropper, Owens' achievements on the track were remarkable. But their global impact was even bigger. He shot to fame by breaking three world records and tying a fourth at a collegiate track meet in Michigan in 1935 in what was called "the greatest 45 minutes ever in sport". But it was at the 1936 Berlin Olympics that Owens' star shone brightest. He won an unprecedented four golds in the 100m, 200m, 4x100m and long jump, to the undisguised fury of Adolf Hitler, who had planned that the Games would be a showcase of supposed Aryan supremacy.

PELE: The only player ever to win three soccer World Cups, but leading Brazil to glory in 1958, 1962 and 1970 only partly defines the man credited with earning the sport its reputation as "The Beautiful Game". The talismanic striker's 77 goals from 91 games for his country were scored with a blend of brilliance and grace. Named World Player of the Century and one of Time magazine's 100 most influential people of the 20th century.

MICHAEL PHELPS: Not always the poster boy for his sport but the superstar swimmer is nevertheless the most decorated Olympian ever, his remarkable 23 gold medals accrued over five Games unlikely to ever be topped. Emerged from post- London Olympic retirement to collect five golds and a silver in Rio at age 31 to boost his overall tally to 28 medals - and his legendary status. Has again hung up the speedos - for now.

KELLY SLATER: The surfer's record 11 world championships came either side of taking a hiatus from the sport in 1998, the American returning to dominate his younger rivals into his 40s. Slater's reach and talents, though, stretch far beyond the water. He is a crusader and fundraiser for suicide prevention and appeared in 24 episodes of the hugely popular 1990s TV show 'Baywatch'.

-AAP