The Red Devils beat Chelsea in midweek with Rashford, 26, benched having only scored two goals this season.
An impressive display in that 2-1 win means it is likely that Antony and Alejandro Garnacho will be given the chance to keep their places against Bournemouth on the weekend but Ten Hag believes Rashford will yet prove his worth to the team.
The Dutchman told reporters: "Rashford is an incredibly good player.
"You can't do [the whole season] with 11 players, also he can't play every game.
"He's not in this moment in the form he was last year but I am sure he will get there."
Ten Hag also referenced the recent rise of Scott McTominay and Harry Maguire, who have scored six goals this campaign and won the Premier League's November Player of the Month awards respectively.
The United boss is confident that Rashford can perform a similar turnaround, if he has the right mental strength.
He continued: "[It's like] what I said about Scott McTominay and Harry Maguire, it's up to them.
"The team will always line themselves up and the best players will form together and the best team will play."