Gonzalo Higuain has admitted to Chelsea boss Maurizio Sarri that he has struggled to adapt to the Premier League.

Striker Higuain retired from international duty on Thursday, bringing down the curtain on an Argentina career comprising 31 goals in 75 caps, an appearance in the 2014 World Cup final and Copa America finals in 2015 and 2016.

The 31-year-old joined Chelsea on loan from Juventus in January, scoring three goals in seven Premier League appearances.

Now Chelsea boss Sarri has called on Higuain to hit top form to spearhead the Blues' final Premier League top-four tilt, starting at Cardiff on Sunday.

"He said to me that it's difficult, because the physical impact of the defenders here is really very strong," said Sarri.

"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.

"And so I think that he needs time, but we have no time. So we need him at his top level in the last two months."

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 is really very difficult to get used to the Premier League in only one, two months."

Ross Barkley scored twice in England's 5-1 win in Montenegro on Monday, in a performance to underline his rich potential for both club and country.

The former Everton midfielder had to battle to shake off a long-term hamstring injury after joining Chelsea in January 2018.

But now Sarri believes the natural "fighter" has proved himself crucial to Chelsea's plans.

"He's improved a lot tactically, also physically I think, because in the last season he played only 200 minutes.

"And so he needed to stay on the pitch. Fortunately now he's going very well.

"He's improved a lot, and he's a very, very good player. He's a fighter, he's able to fight in every match."