Chelsea manager Jose Mourinho is confident that Diego Costa will return to scoring ways once he has 'improved' his condition.

Four games have passed since the Brazil-born Spain international last scored for the Blues.

Following stints on the sidelines with injury and illness, Mourinho believes that Costa is not fully fit, which is therefore hampering the striker's goal threat.

"For me, the problem is not the goals," the Daily Star quotes Mourinho as saying. "They will come as a consequence of his condition.

"He has to improve his condition. He was injured and had many doubts because he went a long time without training.

"Obviously that must have an effect on a player in the way he runs, the way he moves and in his coordination. I don't think there is a problem but he has to recover."

Costa has scored 11 Premier League goals for Chelsea so far this season.