Antonio Conte discussed Romelu Lukaku following Inter's loss to rivals Juventus on Sunday.
Inter head coach Antonio Conte said star striker Romelu Lukaku must train more to be in great shape due to his physique.
Lukaku experienced a quiet game as Inter suffered a 2-1 loss to Serie A rivals Juventus in the Derby d'Italia at San Siro on Sunday.
A club-record signing from Manchester United before the transfer window shut, Lukaku returned to the line-up after missing Wednesday's Champions League defeat against Barcelona due to a muscular problem.
Asked about Lukaku, Conte told reporters: "Romelu is definitely a player that must train more, because being a player with a massive body he needs to train, to play, to be in great shape.
"In this beginning of the season he had this back issue, now he's been dealing with this other quadricep issue since the game against Lazio.
"But I think he gave everything, it's inevitable that against Barcelona we didn't have Lukaku and it was important to have him. And we didn't have him.
"However, Romelu as well was very committed today, he tried to do his best, and now let's hope he can leave these little issues behind him and be at his 100 per cent."
Lukaku has scored three goals for Inter since arriving from United for a fee understood to be €80million (£73m) in August.