Chelsea manager Jose Mourinho has revealed that as many as five players could miss this weekend's trip to Selhurst Park to take on Crystal Palace.
It has been well documented this season that Costa struggles to play more than one game per week having suffered with a hamstring problem.
Mourinho said Costa is a big doubt for the game revealing he gave him two days off on international duty, only for him to report to training on his day off. The Chelsea boss replied with 'no comment' when asked if it was for treatment.
Reflecting on last season's loss to Palace, Mourinho said that Palace - then managed by Tony Pulis - were better than them in 'every way'.
He said: "My lesson in that specific game was not a lesson because it was one of these games I lose and I deserve to lose.
"So I know why I lose, that doesn't give me a lesson. I accept that in a normal way and it is easy to analyse. Last season we lost there because they were better than us in every way."
Despite having a five point lead at the top of the table at this early stage of the season, Mourinho is not getting complacent - saying there are five teams, including his own that can challenge for the Premier League title.
He outlined Manchester City, Manchester United, Arsenal and Liverpool are potential candidates to become Champions - with nine points currently covering all five teams.