Chelsea defender David Luiz reportedly believes that he is being punished by boss Antonio Conte due to his close friendship with former teammate Diego Costa.

The Brazil international was surprisingly left out of the Blues' matchday squad to face Manchester United at the weekend and told to train alone on the morning of the game.

Conte cast further doubt over Luiz's future at Stamford Bridge when admitting that he is unsure if there will be a place for him in the side this season.

According to The Times, Conte was also upset with the conduct of Gary Cahill and Cesc Fabregas following last week's heavy loss to Roma, but Luiz was the player most seriously punished.

The report suggests that the former Paris Saint-Germain ace is concerned that his close association with Costa played a big part in his manager's decision, having attempted to play peacemaker between the two men earlier this year.

Conte informed Costa via text at the end of last season that he was no longer wanted at the club, which is said to have left certain squad members - including Luiz - unhappy.