Marcelo told Neymar that he was better than Kylian Mbappe during Real Madrid's 2-2 draw with Paris Saint-Germain in the Champions League on Tuesday.
The Brazilian, who has been plagued by injury problems since the summer, played in the Champions League for the first time this season during an entertaining affair at the Bernabeu.
Speaking in the tunnel at half time, Marcelo can be overheard saying to Neymar: "You're a better player than [Kylian] Mbappé."
Neymar has been heavily linked with a return to Barcelona next year after openly pushing for a move to Camp Nou over the summer.
Mbappe, on the other hand, is said to be a main target for Zidane, who recently spoke effusively of the 20-year-old.