The 30-year-old Brazil worldwide fears for his future at the club and believes his relationship with Costa could be used against him as Luiz tried to act as peacemaker between Conte and the Spain global over the summer.
Conte insisted the decision was tactical and not because of a row between the pair.
The latest big name to find himself on the wrong side of Conte, Luiz was left out of Chelsea's squad entirely for Sunday's win over United despite being fit, with 17-year-old Ethan Ampadu taking a spot on the bench ahead of him.
After spending two seasons on loan at Borussia Monchengladbach, Christensen has waited patiently for his chance and has now started games against both Manchester City and Manchester United at Stamford Bridge, the latter coming at the expense of Luiz, who was dropped from the squad completely.
Having recently claimed Luiz was the club's best defender, Conte said that "can change" and was adamant the call was "only a tactical decision".
But The Guardian report that Conte will permit Luiz to return to full training with the rest of the first team squad who are not involved in internationals on Wednesday afternoon. It's normal. I have to make the best decision for the club, not for a single player.
"Christensen came in yesterday and played very, very well indeed in a massive game". "We played with great energy, passion and enthusiasm".
According to the Daily Mirror, "Luiz paid the price for questioning Conte's tactics in a team meeting last week".
"When you let players get away with things, other players sense that, and then you may have five or six players against you".