Southampton defender Toby Alderweireld says he must be at his best today against Chelsea.

Alderweireld will likely be one of the men assigned to marking Spain international Diego Costa, and he knows how tough a task shackling the £32m hitman will be.

"It is very difficult, because he is fast, he is strong, he has technique," said the on-loan Saints star.

"He can score goals, is good with his head, so I have to be at my best to stop him."