Talks between the player and the club have stalled amid speculation surrounding a potential summer bid from the Spanish giants.
Real Madrid were 3-0 up at half-time when they replaced most of their starting line-up, including Cristiano Ronaldo.
"At the moment he is really very keen, so I think that he can play a really very good season, or the last part of the season".More news: Senate panel approves Trump's attorney general nominee
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Sarri said: "I think we will be able to fight for the top four this season".
"However, he needs to make a decision before next summer because he hasn't renewed his contract".
"I've only played two games with Higuain and I know we can do something great together, not only with him but also with the other strikers, the other winger".
"He is already 28 years old and this would be the flawless moment to leave, it would be a very personal decision though".
"I'm hopeful I will get back to that level we had before, this is the idea".
"I like to be "the star" but I like also when I can pass the ball to another for him to score, and it is not just about me". The Brazilian has been one of the few leading lights in a relatively poor season for the Toffees thus far, and has emerged on the radar of some of Europe's biggest clubs.