Celtic's Hatem Abd Elhamed has tested positive for Covid-19 while on international duty.
The defender fell ill after playing for Israel against the Czech Republic on Sunday, just days after team-mate Nir Bitton's positive result.
It means the pair will miss Saturday's Old Firm match against Rangers along with James Forrest and Ryan Christie.
Elhamed, 29, will now have to self-isolate for 13 days before returning to training.
Odsonne Edouard also tested positive last week while on under-21 duty with France and the striker's period of self-isolation could make it difficult for him to be ready in time for the weekend.
"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," said a Celtic statement.
"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."
- Credibility of international football not in question - Clarke
- Bitton rose off wheelchair to face Scots
On Wednesday, Christie was instructed to self-isolate after being deemed to be a contact of Southampton's Stuart Armstrong.
The former Celtic midfielder tested positive before Scotland's play-off semi-final win at home to Israel, a game in which Bitton played.
"Hatem Abd Elhamed and another team staff member were found positive in the coronavirus inspection conducted this morning by the Israeli team. All other team players and teams were found negative," an Israeli spokesman told BBC Scotland.
On top of these developments, manager Neil Lennon has a number of injury concerns.
Scotland winger Forrest is out with an ankle stress fracture, 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, although he is expected to make the first Old Firm derby of the season.