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He said his estimate is based on feedback from Dr Anthony Fauci, the director of the National Institute of Allergy and Infectious Diseases.
The league most recently had been aiming for a Christmas Day start - the day is an annual festival of games for fans - but that apparently won't happen
"My best guess is even though it'll be the 2020-21 season, that the season won't start until 2021," Silver said.
Even then, without a COVID-19 vaccine and the coronavirus still spreading across the United States, much remains to be determined, Silver said. Despite the uncertainties, the league's goal is to play an 82-game regular season, at home arenas, with some fans in the stands.
"There's still a lot that we need to learn in terms of rapid testing, for example. Would that be a means for getting fans into our buildings?" Silver said. "Would there be other protections from the things that we are learning in Orlando currently on the campus down there?
"And clearly learning from a lot of other sports with what baseball is currently doing and what football is doing and what college sports have begun playing. There is a lot of new information in the marketplace that we have begun looking at. But the goal is to play a standard season."
The NBA became the first pro league to suspend play amid the pandemic, doing so on March 11. The league finished a shortened season in a bubble at the ESPN Wide World of Sports Complex near Orlando and is nearing the end of the playoffs - with no positive COVID-19 tests.
Despite the success of the bubble model, Silver said the NBA would prefer to keep teams in their home arenas for a variety of reasons, which include keeping players with their families, revenues produced through ticket sales and the high cost of sequestering the players away from home.
Also still to be determined would be the frequency of COVID-19 testing for players and staff and whether travel would be modified.
Silver said the end of the NBA season next year could overlap with the Tokyo Olympics, scheduled for July 23-August 8, which could alter the makeup of the US team.
"There are a lot of great U.S. 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," he said.