The NBA postponed Sunday's game between the Boston Celtics and visiting Miami Heat, just two hours before tip-off, due to the league's health and safety protocols.
Boston were going to have to face Miami with the NBA minimum of eight players but in the end, due to ongoing COVID-19 contact tracing, the league said the Heat did not have the required eight available players to proceed with the game.
No make-up date was announced.
A Miami player returned an inconclusive COVID-19 test while the Heat announced previously on Sunday that guard Avery Bradley would miss the game due to the NBA's pandemic protocols.
The nine unavailable Boston players due to COVID-19 protocols were Jayson Tatum, Jaylen Brown, Javonte Green, Semi Ojeleye, Grant Williams, Robert Williams III and Tristan Thompson - while Kemba Walker (knee) and Romeo Langford (wrist) are out with injuries.
The Celtics seven is the most any team has been without because of virus-related issues so far this season but does not necessarily mean any of the affected Celtics tested positive.
The game is the second this NBA season to be postponed due COVID-19 and other factors.
The scheduled season opener for the Oklahoma City Thunder and Houston was postponed on December 23 because the Rockets did not have enough eligible players to play.
In soccer, Manchester City manager Pep Guardiola confirmed striker Sergio Aguero is self-isolating after being in close contact with someone who tested positive for COVID-19.
Aguero was expected to start in their FA Cup third-round tie win over second-tier Birmingham City on Sunday but did not feature in the matchday squad.
"I don't know exactly because he has been tested like all of us six times in the last 10-15 days so it is negative," Guardiola said of Aguero.
"Today I think he was negative too but the protocols say in some cases isolate and in other cases we still play football.
Meanwhile, Tottenham Hotspur manager Jose Mourinho is preparing for his side's Premier League game at Aston Villa on Wednesday.
The match is understood to be in doubt after a mass outbreak of coronavirus at Villa, with 10 first-team players struck down with the virus.
The midlands club played their youth team in their FA Cup loss to Liverpool on Friday night.
However, when asked when he expects his Spurs to next play Mourinho said: "Wednesday."
Asked whether he thinks the Villa game will go ahead he replied: "Yeah.
"Nobody told me that I'm not going to play so (on Monday morning) we start to prepare for that game, and the same Tuesday unless somebody tells us different."
In Scotland, Celtic said on Sunday one of their players had tested positive for COVID-19, two days after they returned from their six-day warm-weather training camp in Dubai.
The Scottish champions did not say if the infected player was part of the squad that travelled to the UAE.