Nick Kyrgios has pulled out of his proposed US Open mixed doubles pairing with Naomi Osaka, casting doubt on his participation in the singles.
Kyrgios' absence was revealed when the US Tennis Association released the draw for the controversially remodelled event, which also confirmed fellow Australian Alex de Minaur's plea to be included with British fiancee Katie Boulter had been rejected.
Kyrgios has been troubled by injuries for three years and recently posted his knee was "cooked".
World No.8 De Minaur, who had asked for a wildcard "pretty pretty please" via social media, is the highest-ranked man not in the event.
This was despite several other withdrawals, which left new pairing Jessica Pegula and Jack Draper as the top seeds after both their planned partners pulled out.
British men's world No.5 Draper was due to play with Paula Badosa and women's world No. 4 Pegula with fellow American Tommy Paul.
There could yet be further withdrawals. The event begins Tuesday (local time) with the first round and quarter-finals being played then.
Yet Carlos Alcaraz and Jannik Sinner met in the final of the Cincinnati Open in Ohio on Monday, and Sinner quit at 0-5 down in the first set, apparently due to illness.
Italian Sinner is due to partner, in another new pairing, Katerina Siniakova. The Czech women's doubles No.2 has replaced Emma Navarro as partner of the men's singles world No.1. Whether he will be recovered enough to do so remains to be seen.
That is unlikely to help de Minaur however as Boulter is currently playing in a tournament in Cleveland, unless she is knocked out early.
Spaniard Alcaraz is scheduled to play with Emma Raducanu.
French veteran Gael Monfils, who partnered Kyrgios in the DC Open in Washington recently, has replaced him as Osaka's partner.
Another eye-catching duo are 45-year-old Venus Williams and compatriot Reilly Opelka.
They are among eight wildcards, with the other eight pairings selected on the basis of combined singles rankings - thus Draper and Pegula as top seeds.
The qualification policy is just one reason why the event, designed to attract attention of fans, sponsors, television and social media, is controversial.
Prizemoney has been increased five-fold to $US1 million ($A1.5 million) but only four games will be required to win a set in matches before Wednesday's final, with no-advantage scoring (four points will be needed to win a game) and 10-point match tiebreaks instead of a third set throughout.
Last year's US Open mixed doubles champions, Sara Errani and Andrea Vavassori have dismissed the new format as a "pseudo-exhibition focused only on entertainment and show" that would shut out true doubles players.
Having been given a wildcard they will have the chance to make their case for doubles specialists on court with their first match against No.2 seeds Elena Rybakina and Taylor Fritz.
US OPEN MIXED DOUBLES DRAW:
* Jessica Pegula/Jack Draper (1) v Emma Raducanu/Carlos Alcaraz
* Olga Danilovic/Novak Djokovic v Mirra Andreeva/Daniil Medvedev
* Iga Swiatek/Casper Ruud (3) v Madison Keys/Frances Tiafoe
* Naomi Osaka/Gael Monfils v Caty McNally/Lorenzo Musetti
* Katerina Siniakova/Jannik Sinner v Belinda Bencic/Alexander Zverev
* Taylor Townsend/Ben Shelton v Amanda Anisimova/Holger Rune (4)
* Venus Williams/Reilly Opelka v Katarina Muchova/Andrey Rublev
* Sara Errani/Andrea Vavassori v Elena Rybakina/Taylor Fritz (2)
(seeds in brackets)
