In the latest challenge for a major North American sports league trying to navigate the pandemic, the N.B.A.’s Philadelphia 76ers remained in New York on Friday to undergo contact tracing and coronavirus testing after one of their players learned during a game against the Nets on Thursday night that he had tested positive.

The positive test result was returned while the player, Seth Curry, was on the Sixers’ bench during the first half of their loss to the Nets at Barclays Center. The game was allowed to continue, raising questions about the league’s health and safety protocols as it plays without the restricted setup it used to finish last season in Florida.

The Sixers lost, 122-109, and a full evaluation to determine whether Curry had been in close contact with any Sixers players or staff members began in earnest the next morning — after the Nets had flown to Memphis for their next game.

The 76ers will need eight players in uniform to go ahead with Saturday’s scheduled 3 p.m. game against the Denver Nuggets in Philadelphia, but it was unclear Friday night whether they would have enough players to avoid the league’s second postponement of the season.

With the team still in Manhattan as of the N.B.A.’s injury report at 8:30 p.m. Eastern time on Friday, seven Philadelphia players (Joel Embiid, Danny Green, Tobias Harris, Shake Milton, Vincent Poirier, Paul Reed and Matisse Thybulle) were listed as questionable because of the league’s health and safety protocols.

Four other Sixers — Curry, Terrance Ferguson (personal reasons) and the injured duo of Mike Scott and Furkan Kormaz — have already been ruled out of the game. The Sixers have a 17-man roster

Curry, held out of Thursday’s game with an ankle injury, was removed from the Sixers’ bench and placed in isolation after being notified of the positive test during the first half, according to two people familiar with the circumstances who spoke on condition of anonymity because they were not authorized to discuss the details publicly.

“An initial positive test received during a game, when a player has already tested negative that day, results in the player’s immediate removal but does not trigger the cancellation of a game,” said David Weiss, the league’s senior vice president for player matters.

Before Thursday’s game, Curry had taken two daily coronavirus tests as required by the N.B.A.’s health and safety protocols — one rapid polymerase chain reaction test and one lab-based P.C.R. test.

Weiss added: “The testing strategy we have implemented of two daily P.C.R. tests creates a process that aims to identify an infected individual before they become infectious to others. Combined with our data that analyzes contact time and distance during on-court play, our experts believe that the game can safely proceed in these circumstances.”

Major League Baseball faced a similar challenge of a positive test result received during competition, in Game 6 of the World Series between the Los Angeles Dodgers and the Tampa Bay Rays in October. The Dodgers’ third baseman, Justin Turner, learned during the seventh inning that he had tested positive, and was pulled from the game before the start of the eighth inning. The game was not stopped then, either, and Turner later apologized for returning to the field to celebrate winning the championship with his teammates.

Curry’s rapid test came up as negative, allowing him to be on the bench with a mask, according to one of the people familiar with the situation. The 76ers then received the result of his lab test, which was positive, and took him to an isolated room at Barclays Center as play continued. He left the arena separately from the rest of the team.

The Nets still played the Grizzlies, as scheduled, on Friday night. Nets Coach Steve Nash said before the game that he and his players “weren’t aware” of Curry’s positive coronavirus result as they played the Sixers, but he added that since then “the talk or chatter about it amongst our team was pretty minimal.”

On Thursday, Curry had been seated on the front row of Philadelphia’s bench in the first quarter against the Nets in street clothes, with the assistant coach Sam Cassell to his right and, for portions of the quarter, Philadelphia’s star center Joel Embiid to his left.

After the game, Embiid, who recently became a father, told ESPN that he planned to quarantine from his family until he was sure that he did not have the virus.

The Washington Wizards, who played Philadelphia on Wednesday night, played the Celtics in Boston on Friday night. The Celtics announced earlier in the day that three rotation players — Tristan Thompson, Grant Williams and Robert Williams III — would miss that game because of possible exposure to the coronavirus. Other top players in the league have also been in quarantine, including Kevin Durant of the Nets, despite not reporting a positive coronavirus test.

Players are required to quarantine for at least seven days if they are exposed to someone who tests positive. If a player tests positive, he could be required to isolate for at least 10 days. Several players have had to quarantine since the season began Dec. 22, but only one game has been derailed: Houston’s season-opener against Oklahoma City on Dec. 23 was postponed when the Rockets could not field the league’s minimum requirement of eight players.

The N.B.A. announces the results of the leaguewide coronavirus testing weekly and said Thursday that four players out of 498 tested since Dec. 30 had tested positive. Last week, the league announced zero confirmed positive tests out of 495 players tested.

According to the N.B.A.’s protocols, a positive test requires a team to “notify any close contacts of the confirmed positive case of their status and appropriate next steps,” including retesting or quarantine. A player that has tested positive must isolate for at least 10 days or return two consecutive negative tests at least 24 hours apart before he can take steps to return to play, such as working out by himself when no other players are present.