Speaking during a panel discussion on CNN, Silver said the league hoped next season would see a full 82-game schedule with teams playing before fans inside their home arenas.
But the NBA supremo said for that to happen, the start of the season would need to be pushed back from December to January.
"My best guess is even though it'll be the 2020-21 season, that the season won't start until 2021," said Silver, who based his viewpoint on feedback from Anthony Fauci, the head of the National Institute of Allergies and Infectious Diseases.
"We said the earliest we would start is Christmas of this year. But the more I'm learning and listening to Dr. Fauci this morning, I continue to believe we're going to be better off going into January. The goal for us next season is to play a standard season."
The NBA halted its 2019-2020 season in March as COVID-19 sent sport in North America grinding to a standstill.
The league restarted the season inside a secure "bubble" in Orlando, Florida in July, with teams based at a single location.
If the league does not start until January, it means the climax of the NBA season would almost certainly clash with the rescheduled Tokyo Olympics, due to take place from July 23 2021.
Silver indicated that the scheduling clash would likely see a US team stripped of top talent at the Olympics.
"It would be tough for us to make a decision in January based on the Olympics happening on schedule when that is so unclear," Silver said.
"I just add that there are a lot of great US players. We may be up against a scenario where the top 15 NBA players aren't competing in the Olympics. But other great American players are competing."
Silver's comments came as the United States registered its 200,000th death from COVID-19, which has also infected more than 6.8 million Americans.