Tributes have poured in across the sporting world for Serena Williams following her apparent US Open swansong on Friday, though the 23-time grand slam winner has kept the door ajar on a shock return.

The American, widely considered one of the greatest sportspeople of all time, suggested she would step away from top-level tennis following the tournament at Flushing Meadows.

Following a 7-5 6-7 (4-7) 6-1 loss to Australia's Ajla Tomljanovic in the third round, her journey now looks to be over – though the 40-year-old admittted "you never know" when asked about future appearances.

Her likely last dance, however, has prompted an outpouring of glowing tributes from far and wide, with a host of major names paying their respects to an unparalleld career.

15-time major-winning golfer Tiger Woods called her "the greatest on and off the court" while four-time NBA champion LeBron James hailed her as "so dope".