Real Madrid captain Sergio Ramos has tested positive for coronavirus.
The veteran centre-back, who has a storied history with Liverpool, had already been ruled out of his side's Champions League clash with Liverpool due to a calf injury but he is now set to isolate as he recovers from Covid-19 before continuing with his rehabilitation.
The La Liga giants, who head into the quarter-final second leg with a 3-1 home lead, released a statement about Ramos on their website on Tuesday morning to relay the news.
Elsewhere, Ramos' centre-back partner Raphael Varane will miss the game against Jurgen Klopp's side having also contracted Covid-19.
Zinedine Zidane will also send his charges into battle at Anfield on Wednesday without right-back Lucas Vazquez, who suffered a season-ending knee injury against Barcelona this weekend, and fellow full-back Dani Carvajal.
Eden Hazard, the former Chelsea forward, is also still recovering from an ankle problem.
Meanwhile, Spanish publication AS report that dynamic midfielder Fede Valverde is a "doubt" for the game having sustained a foot injury in El Clasico while the media outlet speculate that the instrumental Toni Kroos could miss out due to being withdrawn from their 2-1 win over Barca in the 72nd minute in "some discomfort".
Both players have been included in Madrid's 23-man travelling party, however, having recovered quickly to make the squad.
It remains to be seen what shape they may be in to start the game, though, given Valverde was on the bench in the first-leg against the Reds having only recently returned from injury previously.
