Santiago Solari has insisted Marcelo is the "second captain" and "100 per cent Real Madrid" as he stood by the under-fire full-back.
An integral part of Madrid's three successive Champions League titles, Marcelo has struggled for form this season – though he did start in Wednesday's 1-1 Copa del Rey semi-final first-leg draw away to rivals Barcelona.
Marcelo – who has been tipped to reunite with Cristiano Ronaldo at Juventus – has only made 12 La Liga appearances this term, and 23 in all competitions.
The 30-year-old Brazilian, however, received the backing of Madrid head coach Solari following the stalemate at Camp Nou.
"Marcelo is the second captain," Solari said.
"He is 100 per cent Real Madrid and we want to see his best form."
While Marcelo has failed to convince in 2018-19, countryman Vinicius Junior has thrived under Solari at the Bernabeu.
Vinicius was in the starting XI again for the trip to Barcelona and the 18-year-old – who arrived from Flamengo in the off-season for a reported €46 million – earned praise from Solari after the match.
"I'm not surprised [about his development], I know him, and I know his way of playing football," Solari said.
"It's amazing that a boy of 18 years of age is progressing the way he is. Some credit also has to go to his team-mates, who support him and allow him to play."
Madrid made a dream start to the Clasico showdown at Camp Nou, where Lucas Vazquez opened the scoring after just six minutes.
Barca, however, equalised via Malcom near the hour mark to leave the semi-final tie evenly poised ahead of the return fixture in the Spanish capital on February 27.
"We always want to win games and we had chances to score a second. We're happy with what we've done today," Solari said.
"We're taking it step by step. The game just finished. We've got a few days to work hard. We have to see how Marcos Llorente is and I have a press conference before the next game.
"This is a really nice competition, we are fighting to win it and we'll now look at the next La Liga match."