Antonio Conte has warned that every Chelsea player is at risk of losing his place in the starting line-up after David Luiz was left out of his squad for the 1-0 victory over Manchester United on Sunday, 5 November, due to "tactical" reasons.
David Luiz had been a crucial player for the Italian boss last season since returning to Stamford Bridge from Paris Saint-Germain in the final days of the 2016 summer transfer window.
However, Conte decided to leave him out of the matchday squad to face United, amid reports claiming that the relationship between the pair had grown tense.
Andreas Christensen took his place in his three-man defence alongside Cesar Azpilicueta and Gary Cahill, with 17-year-old Ethan Ampadu making the bench.
"It was only a tactical decision. This can happen to any one of my players. If I see they are not in good form, it's normal. I have to put my face in every situation, and sometimes make important decisions. Today, I did this, and Christensen played an amazing game. I was very happy for this," Conte said in the press conference following the win over United.
"It's very simple. The coach has to make the best decision for the team. Tonight, the best decision for the team was to play with Christensen and to have Ampadu on the bench, young players, really good players for the present and the future. Maybe in the future I can decide in a different way, or continue in this way. I must take the best decision for the club, not for a single player. Sometimes, I can make mistakes or sometimes I can do the best thing."
Last season, Conte also left Costa out of the Chelsea squad for a 3-0 victory over Leicester City on 13 January, amid suggestions the striker had had a training ground row with the boss over his fitness.
The Spanish striker stayed at the Premier League champions until the end of the season, but was sold to Atletico Madrid in September after being told that he was not in Conte's plans for the new campaign.
Pressed by BBC about whether Luiz has a future at Chelsea, the former Juventus manager added, "He has to work really hard, otherwise he is on the bench or in the stands. I don't know. Christensen is the present and the future for Chelsea."