Pittsburgh Steelers quarterback Ben Roethlisberger and three other players are in isolation after a Covid-19 case involving team-mate Vance McDonald, the team announced on Tuesday.
Roethlisberger, offensive lineman Jerald Hawkins, running back Jaylen Samuels and linebacker Vince Williams have all been placed on the Covid-19/reserve list.
The decision means they must remain isolated for five days and will not be permitted to train in the Steelers' UPMC Rooney Sports Complex.
The players will be required to undergo daily Covid-19 testing and must return negative results to be eligible for the Steelers' upcoming clash with the Cincinnati Bengals at the weekend.
Steelers coach Mike Tomlin said he expects all players will be available for selection provided they passed testing.
"Those guys will be working remotely throughout the week and testing daily," Tomlin said.
"As long as their tests come back negative, we believe that all four guys, will be made available to us on Saturday.
"It will give their bodies some much-needed rest. We're optimistic that those guys will be their normal selves this weekend."
The development comes after tight end Vance McDonald tested positive for the coronavirus on Monday.
Under NFL contact-tracing protocols, individuals deemed to have been at risk of high exposure to anyone with Covid-19 must isolate for five days.
McDonald had missed a training session last week after complaining of feeling unwell, but joined the Steelers and played in Sunday's 24-19 road victory over the Dallas Cowboys.
The Steelers are the only remaining unbeaten team in the NFL this season with eight wins out of eight, the best start to a season in franchise history.