Steve Clark has been credited as a major influence on Chelsea's success under manager Avram Grant.
The Observer says Clarke has assumed greater responsibility, Jose Mourinho's former assistant conducting most of the training, pre-game presentations on opponents and team talks.
"Steve is doing what he needs to do," says Grant. "Each training session is different - sometimes he makes this training, sometimes that. I will not say specifically, but he is very important for the club."
Last month Clarke's salary was doubled, though only until the end of the season and still to a level far below those of Grant and Ten Cate.
"Without Steve things would have fallen apart," says one source.