Manchester City pair Gabriel Jesus and Kyle Walker have tested positive for Covid-19, the Premier League club have announced.
Two members of staff at the club have also returned positive tests.
Both players featured in City's 4-1 Carabao Cup win over Arsenal on Tuesday, with City due to host Newcastle in the Premier League on St Stephen's Day.
A club statement said: "Manchester City FC can confirm that Gabriel Jesus, Kyle Walker, and two members of staff have tested positive for Covid-19.
"All four personnel will now observe a period of self-isolation in accordance with Premier League and UK Government protocol on quarantine.
"Everyone at the Club wishes our colleagues a speedy recovery over the Christmas period ahead of their return to work, training and competition."