Ramos is the second case of coronavirus detected in the Real Madrid squad in a week. French defender Raphael Varane tested positive last Tuesday.
From a 10-point gap at the close of January, Atletico Madrid have seen their lead cut down by Real Madrid and Barcelona. A Clasico win would help the two's title ambitions further.
LaLiga: Karim Benzema's record for fastest goal, Lionel Messi's prolific numbers and more records from El Clasico
Here are eight records that have defined this era of the El Clasico and the classic rivalry between Real Madrid and Barcelona.
Both players' contracts are up at the end of the campaign and Messi is yet to commit to a new deal with Barca after trying to force an exit last summer.
Vinicius and Marco Asensio both profited in the first half after darting behind Liverpool's makeshift back-line before a simple move from a throw-in gave Vinicius a simple finish in the second.
Champions League: Real Madrid defender Raphael Varane tests positive for COVID-19 ahead of Liverpool clash
Madrid are already without the injured Sergio Ramos, meaning Nacho Fernandez and Eder Militao are the only fit central defenders left in Zinedine Zidane's squad for the game against Liverpool in the Spanish capital later on Tuesday.
Champions League: Liverpool boss Jurgen Klopp insists he's not on revenge mission against Real Madrid
Klopp was asked if he would ever fancy swapping Merseyside for Madrid, but said he is more interested in the Mallorcan sun if he ever moved to Spain.
"I think my team has been underestimated," said Zidane in a press conference on Monday. "We are going to fight for everything. We have had difficult moments this season and now we are better but it doesn't mean anything tomorrow."
Real Madrid might have taken more comfort from Liverpool's problems were they not confronting their own period of introspection.
Real Madrid defender Sergio Ramos suffers calf injury ahead of Champions League tie against Liverpool
The veteran centre-back made his 180th international appearance in Spain's World Cup qualifying win over Kosovo as a late substitute, but said he felt the problem after the match.
European football matchday: Manchester City face Everton in FA Cup; Real Madrid visit Celta Vigo without Sergio Ramos
Real Madrid did not indicate why Sergio Ramos will not travel to northwest Spain for the match against Celta Vigo.
His skills were evident from the start but Vinicius Junior has often struggled to turn great plays into goals.
Sergio Ramos turns 35 at the end of this month and a parting this summer would offer immediate relief for a club now seeking financial recovery.
In 16 seasons with Madrid, Ramos has helped the club win four Champions League titles, five Spanish leagues and two Copa del Reys, with both his hardnose defending and some timely goals.
LaLiga: Eden Hazard is 'going to do very well' at Real Madrid despite injury concerns, says Zinedine Zidane
Hazard has missed Madrid's past seven games with a thigh problem but could return, as could captain Sergio Ramos, against Elche on Saturday, a timely boost ahead of next week's Champions League clash with Atalanta.
The Brazil defender makes it nine players currently on the sidelines for Zinedine Zidane, who called up six youth teamers for Tuesday's 2-0 win over Getafe.
Ramos is expected to be out for six to eight weeks, meaning he would miss both Champions League games, dealing a huge blow to Madrid.
LaLiga: Lionel Messi's future will depend on Barcelona elections and sporting project, says former Real Madrid captain Fernando Hierro
Former Real Madrid defender and captain Fernando Hierro spoke about Lionel Messi, Sergio Ramos and the on-going LaLiga season where Atletico Madrid are in command.
Madrid have won just once in La Liga since October and also lost at Shakhtar Donetsk in the Champions League on Tuesday and must beat Borussia Moenchengladbach next week to advance.
LaLiga: Atletico Madrid edge past Barcelona to earn title boost; Villarreal hold Real Madrid to a 1-1 draw
Yannick Carrasco finished brilliantly from range after mistakes from Gerard Pique and Marc-Andre ter Stegen left the goal gaping but Barca, and a below-par Lionel Messi, failed to respond at the Wanda Metropolitano.