It was a risk to play Diego Costa against Stoke - Mourinho
Chelsea manager Jose Mourinho said it was "a risk" to play Diego Costa after he was injured during Saturday's 2-1 win against Stoke.
Costa replaced Oscar at half-time, with the score 1-1, but lasted only 10 minutes before being forced off with further hamstring trouble.
"If the result was 2-0 he wouldn't play. But I have to risk. My medical department had to risk," said Mourinho.
He said the striker will miss at least two weeks.
It rules the Spain forward out of the matches at QPR on 12 April and against Manchester United at Stamford Bridge on 18 April.
Costa has scored 19 goals since joining Chelsea from Atletico Madrid for £32m on a five-year contract in July last year.
In September, Mourinho revealed that the striker was not able to play more than one match a week because of a hamstring problem.
Costa suffered another hamstring injury against Hull on 22 March and missed Spain's games against Ukraine and the Netherlands.
Mourinho said: "If the medical department decide to take four weeks, it wouldn't happen.
"But no way am I upset with my medical department and I am not unhappy with the will of the player to try and help the team.
"From all the scans two days ago, the muscle and image was completely clean. The player trained twice at 100%. He did much more in training than he did in the match.
"The medical department do fantastic things for us. We will wait for Diego again. Next week Loic [Remy] or Didier [Drogba] will play."
Asked how long Costa would be sidelined for the Chelsea boss added: "For sure a couple of weeks minimum. Let's see what happens."