'Higuain needs to improve mentally and physically'

"I think he needs to improve, physically and mentally. He has to be able to be useful to the team when we are coming to the end of the season," Sarri said of Higuaín.

Released by Juventus after a disappointing six months at Milan, the Argentine striker is looking for his best form at Stamford Bridge. In 11 games with the Blues, he has only scored three goals.

"It's hard to adapt to the Premier League in the first few months, but I think he just needs time," said Sarri, who hopes to beat Pellegrini's team.

Sarri's words have the intention of spurring Higuain on in the final weeks of the campaign and give continuity to his good form for the future.

"Yes, of course I'd like it to continue, but it's up to the club and Juventus. At the moment his situation is not clear," said the Italian coach, who first came across Higuain at Napoli.