Celtic defender Hatem Elhamed will miss Saturday's match against Rangers after testing positive for coronavirus.
The Israel international felt unwell after playing in his country's 2-1 defeat by the Czech Republic in Scotland's Nations League group on Sunday night and has since returned a positive test result.
Elhamed has to enter a 13-day period of isolation and Celtic have expressed more disappointment and frustration after he became the latest player to test positive while on international duty.
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"Celtic Football Club can confirm that Hatem Elhamed has tested positive for Covid-19 while on international duty and is now required to enter a 13-day period of isolation in line with regulations in Israel," read a club statement released on Monday.
"Our medical staff will maintain constant dialogue with him and will provide all required support. Everyone at the club sends Hatem our best wishes and, of course, we hope he makes a full recovery as soon as possible.
"We are, of course, disappointed and frustrated that another player on international duty has tested positive - during an international period which is continuing to present huge challenges for the club.
"During the remainder of this international period, as we have done throughout, we will be maintaining close contact with the relevant international associations, in order to ensure everything possible is being done with regards to the care and protection of our players, something which must be a priority.
"While FIFA regulations determine that clubs are obliged to release players for international duty, going forward we are sure wider discussions will take place around this hugely important issue. We will monitor these discussions closely."
Elhamed's club and international team-mate, Nir Bitton, tested positive on Friday after playing for Israel against Scotland the previous night.
Celtic striker Odsonne Edouard earlier tested positive while away with France U21s, while Ryan Christie was instructed to self-isolate after being deemed to be a contact of former Hoops team-mate Stuart Armstrong while on Scotland duty.
Elhamed, Bitton and Christie will miss Celtic's Scottish Premiership clash with Rangers, while Edouard's period of self-isolation could make it difficult for him to be ready for Saturday's game.
Manager Neil Lennon also has some injury worries ahead of the game.
Centre-back Christopher Jullien has not played for a month because of a back problem, while striker Albian Ajeti missed their previous game against St Johnstone with a hamstring injury, but is expected to make the derby clash.
Winger James Forrest is also out for several weeks with injury.