A game between the New England Patriots and the Kansas City Chiefs that had been scheduled for Sunday was postponed because of positive coronavirus tests on both teams.
The Patriots revealed Saturday that one of their players had contracted the virus.
The NFL's news service reported that star Patriots quarterback Cam Newton and Chiefs practice squad quarterback Jordan Ta'amu had both tested positive. The Chiefs have not publicly commented.
Both athletes have been placed on a reserve-Covid list of players who have either tested positive or who are quarantining because they came in contact with an infected person.
The NFL said in a Twitter statement Saturday that the game will be rescheduled for Monday or Tuesday.
"In consultation with infectious disease experts, both clubs are working closely with the NFL and the NFLPA to evaluate multiple close contacts, perform additional testing and monitor developments," the league said, referring to the NFL Players Association.
"All decisions will be made with the health and safety of players, team and gameday personnel as our primary consideration," the statement said.
A reporter for NFL Network, Ian Rapoport, said in a tweet that both teams' facilities are closed and that contact tracing is being conducted. The NFL "is taking it day-by-day with the game" between the Patriots and Chiefs, based on test results over the next few days, he said.
The Patriots said earlier Saturday that they learned Friday that a player had tested positive.
"The player immediately entered self-quarantine. Several additional players, coaches and staff who have been in close contact with the player received point of care tests this morning and all were negative for COVID-19," the team said in a statement.
Newton, 31, holds the NFL record for the most rushing touchdowns by a quarterback. In 2015, he became the first player in the league's history with at least 30 passing touchdowns and 10 rushing touchdowns in a single season; he was named the NFL's MVP.
Newton began his NFL career with the Carolina Panthers when he was selected first overall in the 2011 NFL draft. He joined the Patriots as a free agent in July, a few months after he was released by the Panthers.
Ta'amu, 22, was signed to the Chiefs' practice squad in April after he entered the NFL as an undrafted free agent in 2019.
It is the latest setback for the NFL. Last week, officials postponed a Pittsburgh Steelers-Tennessee Titans game that had been set for Sunday after several Titans players and team employees tested positive.
Due to the pandemic, nearly all games have been played inside empty stadiums.