Luiz moved back to Stamford Bridge on transfer deadline day from Paris Saint-Germain for £32m – just two years after he was flogged to the French champions for £50m.
The Brazilian’s return has been met by a mixed reaction, with some pundits and supporters questioning his concentration during the latter stages of games.
Marquinhos however, who played with Luiz at PSG and for the national team, believes such criticism is exaggerated and unfair.
“David Luiz as a person and as player is exemplary,” Marquinhos told ESPN Brasil.
“I had the pleasure of working and learning from him, and I tried to learn the maximum I could.
“The life of a player in his position is risky, as the central defender is the last man, he cannot make mistakes; the defender is usually a zero or a hero for his team.
“David was exemplary, and some of the criticism was exaggerated because he brought a lot to the club.”