Gonzalo Higuain has told Chelsea head coach Maurizio Sarri he is finding it difficult to adapt to the Premier League.
Higuain joined Chelsea on loan from Juventus in January, joining up again with Sarri after a productive spell together at Napoli.
But the forward is struggling to reach the same form in a Chelsea shirt, scoring three goals in 10 appearances, and Sarri said: "[Higuain] said to me that it's difficult, because the physical impact of the defenders here is really very strong,
"The referees here are really very different than in Italy, and so it's another football for him, especially for a striker and a goalkeeper, it's really very different."
But with Chelsea four points off an automatic Champions League place with eight games to play, Sarri called on Higuain to rediscover his form for their run in.
He said: "I think he needs time, but we have no time. So we need him at his top level in the last two months."
The Argentine retired from international duty on Thursday after achieving 31 goals in 75 caps and appearances in the 2014 World Cup final and 2015 and 2016 Copa America finals.
Chelsea have appealed against a two-window transfer ban from FIFA, leaving Higuain's future up in the air beyond the end of the season.
Asked if Higuain will be at Chelsea next term, Sarri replied: "I don't know, I'd like to see him at the top in the last two months.
"At the moment only this is really very important. We need Gonzalo at the top. It's not easy I think to get used to this championship.
"The level is different, the way of playing is different, and I think that especially for a striker it is really very difficult to get used to the Premier League in only one, two months."
Chelsea play Cardiff live on Sky Sports Premier League on Sunday.