Santiago Solari 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 – highlighted 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 LaLiga 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 Santiago 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 €46million – earned praise from Solari post-match.
"I'm not surprised [about his development], I know him, and I know his way of playing football," Solari added.
"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.
However, Barca equalised via Malcom approaching 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 LaLiga match."
Solari continued: "It was a beautiful game, with real quality and regular shifts in momentum. It was great to watch for all the fans of any club. We had chances to score in both halves, with Vinicius Junior's effort or Gareth Bale's attempt. It's hard to talk about justice in football.
"Making comparisons is pointless. This game is confirmation that this group of players is working very well. It's an open-ended result, there's a lot of quality out on the pitch and anything can happen at any time."
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