Everton manager Ronald Koeman expects Romelu Lukaku to attract interest from the world's biggest clubs, but he is thrilled to have the striker.
Lukaku, 23, opted to remain at Goodison Park at the end of last season despite interest from Chelsea - his team's opponents on Saturday.
He already has seven goals in nine league games, well on track for a fifth straight campaign with 10 or more goals.
Koeman knows clubs will keep coming back for Lukaku, who is contracted until mid-2019.
"He is a big striker who will always generate interest from big clubs and from bigger clubs than Everton but the boy is 23 and he took the right decision to stay," the Dutchman told UK newspapers.
"He can improve and he needs to improve. That's good because it is very difficult to get a replacement for a player who compares to Romelu, maybe impossible.
"I was a little bit afraid to lose the player."
Lukaku has helped Everton into sixth in the table with seven of their 15 league goals.
Koeman insists the Belgium international will stay until the end of the campaign, despite reports of a January move.
"Maybe we will get the same problem next season. I read some stories in the press about January - no way, no way," he said.
"Bayern Munich, Juventus, [Real] Madrid, Barcelona? He stays until the end of the season at least.
"OK, that needs to be the next step for him and then we as Evertonian people can be proud that he made that step, but let's score goals. That's the best answer he can give on the pitch."