The Frenchman managed just seven goals for United last season and one for Sevilla but Ten Hag insisted the 26-year-old can have a key role to play in his new-look team if his attitude is right.
"I'm sure he can come back even better," Ten Hag said. "I think when he has the right focus and the right motivation and he works hard he will have production because he is a good player.
"I say when he has the right focus and every day delivers much then he will have production and it's up to him."
Ten Hag's United have now scored eight goals in two games on their tour of Thailand and Australia, following up the 4-0 win over Liverpool in Bangkok with a 4-1 victory over Melbourne Victory at the MCG on Friday.
"I don't want to talk about the individuals because I think it was from the start high up the pitch," Ten Hag added.
"The wrong choices and then it ends up like a pack of cards. It's not one individual, it is more the team who made mistakes."
"David trains already, he is back on the training pitch so no big worry." the Dutchman said.
"Raphael Varane is also training but something small and I expect him back on the training pitch."