The Spain international has already scored seven goals in five Premier League games following his £32m switch to the west London side from Atletico Madrid in the summer.
He gives everything for the team. He is a huge player and at the top level in the world
And Luis, who followed Costa from los Rojiblancos to Stamford Bridge, is in no doubt that the 25-year-old will finish as the Premier League’s leading goal-scorer.
“I will not be surprised if he is in the top five of the Ballon d’Or this year and he will deserve it,” said Luis.
“He is going to be a top scorer in England. The team play for him. He decides the games. Sometimes it’s 0-0 and really difficult and he can open these games because he smells a goal.
“That’s why Diego can adapt to any team he goes to. He is doing a great job. I know every game he plays, he gives his best and leaves everything on the field. He gives everything for the team. He is a huge player and at the top level in the world. I am really happy to be with him for the fifth year in the same side.”
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