Venus and Serena Williams suffered defeat for the first time in 18 months on their return to the court on which they won Olympic gold together just over three months ago.
The sisters, winners of Wimbledon as well last year, were beaten in a third set tie-break by Martina Hingis and Monica Seles - playing together for the very first time - in the opening round of the adidas International in Sydney.
Chosen as the showpiece night match under the Centre Court floodlights, Hingis and Seles won 6-4 3-6 7-6 just after 10pm after saving four match points on Venus Williams' serve at 5-6 in the decider. It ended the sisters' run of 22 unbeaten doubles matches.
While Serena has a chance to make amends in the singles, Venus decided to opt out of that and so her next match will be in next week's Australian Open in Melbourne.
She is confident her lack of competitive match practice - her last tournament was two months ago - will not count against her in the first Grand Slam of the year.
"If I'm not ready I should go home," said the 20-year-old, who will stay on in Sydney to practise with her 19-year-old sister.
"It was tough coming back here because the Olympics were so exciting and I was so excited with the whole experience," she added.
Hingis had asked Seles to team up with her after splitting from Anna Kournikova last month and, although unseeded just as the Williams were, they are favourites now to begin their partnership with a title.
"It was such a great match, who could believe it was only first-round doubles?" said Hingis.
Kournikova, now with Austrian Barbara Schett and like Seles a winner both in singles and doubles during the day, spoke in between about the break-up with Hingis - and denied there had been a bust-up.
The pair won nine tournaments together, including the 1999 Australian Open and ending with the Chase Championships in New York last November.