As the Sixers neared the tip of a 115-104 preseason victory over the Brooklyn Nets, Simmons -- fresh off a flight from Los Angeles -- entered the arena to take a COVID-19 test and start the process of returning to a franchise from which he has requested a trade, sources said.
The initial test starts several days of testing required by the NBA to clear him for a return to the team.
According to ESPN's Adrian Wojnarowski, the Sixers were unaware Simmons was flying into Philadelphia Monday.
"I'm going to call Woj and find out what's going on," head coach Doc Rivers joked with the reporters.
Simmons is expected to meet with the organization's leadership starting Tuesday at the team's practice facility, sources said.
Simmons' arrival concluded several weeks of discussions between the organization and Simmons' representative, Klutch Sports CEO Rich Paul, to get Simmons back into the marketplace, sources said.
Simmons had held out in hopes of accelerating a trade. However, under the terms of the NBA's collective bargaining agreement, for each preseason game he missed, he lost roughly $360,000 for failing to show up -- totaling more than $1 million for the three games that he missed. In addition, the Sixers could fine Simmons for missed practices: $2,500 for the first, $5,000 for the second, $7,500 for the third and for every practice after, being left to the discretion of the team, with the ability to go up to $50,000.
Simmons, 25, has four years and $147 million left on his contract.
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Simmons hadn't spoken directly to team officials since a late August meeting in Los Angeles in which he reiterated his desire for a trade, sources said. He had recently become more open-minded about the possibility of ending his time away from the team and reporting to Philadelphia, but the next step will be him committing to not just a return to the city -- but rejoining the team on the court.
The Sixers have canvassed the league throughout the offseason for trades but have been unable to find a deal that would bring them a comparable star they'd want to continue to build a championship contender around All-NBA center Joel Embiid, sources said. Those trade talks would likely continue with a Simmons return, but president of basketball operations Daryl Morey and coach Rivers are hopeful to continue working to convince Simmons on remaining long-term with the franchise, sources said.
ESPN contributed to this report.