The 31-year-old has finally reunited with Maurizio Sarri, with the pair working well during their time at Napoli.
And Hasselbaink says the Juventus loanee must get himself fully fit if he is to impress at Chelsea.
"We know that he (Higuain) knows where the back of the net is," said Hasselbaink.
"The only little worry that I have is he's 31, how fit is he? How fit is he to cope in the Premier League?
Higuain signing will ensure Chelsea finish in top four says Nicol
"We know that the Premier League is the hardest league in the world, physically you have to be right.
"If he is physically right, he will score goals. If he's not he will have a little bit of a problem."
Higuain's best season came under Sarri at Napoli, with the Argentine netting 36 Serie A goals.
A lot has been made of Chelsea’s move for Higuain, with former Blues ace Mark Schwarzer claiming the striker can have a similar impact to Diego Costa.
"He (Higuain) comes across a little bit Costa-esque in terms of (he) likes a bit of a scrap, likes a bit of getting his body on the line," Schwarzer said.
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