Rio de Janeiro: The throne is vacant, should Mack Horton be ready to take his seat where the likes of John Konrads, Kieren Perkins and Grant Hackett have gone before.

On Saturday night in Rio, in one of the final races of a memorable Olympic swimming meet, Horton has the chance to join some of Australia's greatest names in what many still regard as Australia's event.

China's Sun Yang competes during a men's 1500m freestyle heat in Rio on Friday morning. Credit:AP

Now, his arch-rival Sun Yang, the defending champion and world record holder, won't be there to stand in his way.

After a bitter dispute between the pair surfaced prior to the 400m freestyle, won by Horton in an epic dual, the rematch in the longer race was to be one of the features of a controversial week in Rio, where the spectre of doping clouded the results in the water.