Chelsea goalkeeper Thibaut Courtois believes in-form Diego Costa is unplayable, claiming rival defenders do not know how to deal with the Spain international's attacking prowess. 

The 28-year-old has already netted 12 goals in 15 Premier League outings following his winner against West Brom at the weekend to fire Chelsea to the top of the table.

And the striker's fine performances remind Courtois of their time together at Atletico Madrid.

"I remember the year we were champions with Atletico he was very strong, and the year we were champions with Chelsea he was very strong as well," Courtois told the official Chelsea website.

"This season up to now he has scored very important goals. He is really strong on the ball as well and he dribbles past defenders like it is nothing, so he is very strong at the moment and we can only enjoy that and use him as our strength.

"It was a rough time for all the team last year but from January or February Diego was already scoring a lot of goals, and he has just carried that form on.

"The goal against West Brom came from a little mistake by their defender and Diego scored fantastically."