Celtic expressed more disappointment and frustration after Hatem Elhamed tested positive for Covid-19 while on international duty with Israel.
The Hoops defender has to enter a 13-day period of isolation and will miss Saturday's Old Firm clash with Rangers at Parkhead.
The news comes two days after the Scottish champions confirmed that Nir Bitton, Elhamed's Israel team-mate, was also out of the first Glasgow derby of the year after testing positive for coronavirus.
Ryan Christie is self-isolating after being a close contact of Stuart Armstrong, who picked up the virus on international duty with Scotland, while striker Odsonne Edouard contracted the illness while with France Under-21s, but will reportedly return on Friday.
Celtic boss Neil Lennon will also be without winger James Forrest who is out with an ankle injury.
A statement on the club's website read: "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.
"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."
