Chelsea manager Jose Mourinho has called on Diego Costa to improve his fitness as the striker failed to get the better of 32-year old Fabricio Coloccini on Saturday.
The Brazil-born Spain international hit the ground running after signing from Atletico Madrid in the summer, scoring seven goals in his first four Blues appearances.
But he has netted only twice in his last seven, but he has been hampered by hamstring problems.
Mourinho's men suffered their first defeat of the season at Newcastle on Saturday, with Costa again failing to trouble the scorers.
Jose Mourinho: "For me, the problem is not the goals - 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 co-ordination.
"I don't think there is any problem but he has to recover."