Real Madrid duo Thibaut Courtois and Dean Huijsen will miss the Champions League trip to face Olympiacos on Wednesday.
Belgian stopper Courtois "has been diagnosed with viral gastroenteritis" said Madrid in a statement on Tuesday ahead of the match in Athens.
Andriy Lunin is set to fill in for the record 15-time champions, who are seventh in the league phase table.
Huijsen was not included in the squad list for the game published by Madrid on Monday, with Spanish media reporting he suffered a minor muscular issue in the 2-2 La Liga draw at Elche on Sunday.
It leaves Madrid with just one fit natural centre-back available in Raul Asencio, as Eder Militao and Antonio Rudiger are sidelined as well.
However, defensive midfielder Aurelien Tchouameni returned to the squad after a leg injury and he has often featured at the heart of defence when required to in the past.
Madrid have failed to win any of their last three games across all competitions, including a 1-0 defeat by Liverpool in their previous Champions League match.
