CHELSEA star Oscar insists Diego Costa MUST improve if the Blues are to be champions.

Costa is the Premier League's top scorer with 15 goals and Chelsea moved two points clear of champions Man City after their 2-0 win over Newcastle on Saturday.
But Oscar, who scored the opener against the Toon, thinks the Spain striker can do even more for the cause.
The Brazil midfielder, though, insisted the whole team could do better after a blip.

      

"Diego is a fantastic player. This season he has helped Chelsea so much and scored so many goals," he said.
"But we need Diego to play better every game because now Manchester City is second, just two points behind. But not just Diego, we need everyone to play their best."