Chelsea need to sign Romelu Lukaku or Alvaro Morata if Diego Costa leaves the club at the end of the season, according to Jimmy Floyd Hasselbaink.
Costa ultimately stayed with the Blues in the January transfer window after heavy speculation linking him with a lucrative move to the Chinese Super League.
But the Spain international is still being linked with a switch to China at the end of the current campaign, with Tianjin Quanjian still in the race to sign him, while former club Atletico Madrid and Juventus have also been credited with an interest.
If Chelsea's top centre-forward leaves, the club's former striker Hasselbaink thinks Everton's Lukaku - who has reportedly rejected a new contract - or Real Madrid star Morata would be best-suited to replace him.
"Let's not forget he used to be at Stamford Bridge and he's been at a lot of clubs on loan because he needs games and playing time," Hasselbaink told Sky Sports of Lukaku.
"Lukaku has been to West Brom on loan and he's been at Everton and he's done exceptionally well. Exceptional.
"The way that Chelsea are playing, he is, along with Morata, the player you are going to look at to take over from Costa.
"Everton paid, at the time, a lot of money for him but because he has developed that well. Nowadays for players of his stature, you pay that kind of money.
"If you want to have a goalscorer in your team at that age, you have to pay."
Hasselbaink thinks there is already little to separate Costa and Lukaku, but thinks the 23-year-old can get even better if he leaves Everton to re-join Chelsea.
"Is he as good as Costa? I think they are very close," added Hasselbaink.
"They are very similar, he's not as temperamental but he does lead the line and I think he is still going to become better.
"I think he has matured that's for sure, but if you compare Costa and Lukaku they are very similar. If you compare him to Harry Kane, they are totally different.
"With all due respect to Everton, if he does go to Chelsea he will play with better players, so he is going to get better as well.
"Yes the pressure is going to be on him, the shirt will be heavier and only certain kinds of players can handle that and he will have to show that he can.
"But what he has done for Everton, Chapeau, very, very, very well done."