The England international had two golden opportunities to find the back of the net against Manchester City in the Community Shield, but he placed his first effort wide of the post before hitting the woodwork in the second period.
Alejandro Garnacho sent the Red Devils ahead in the latter stages of the game at Wembley Stadium, but Bernardo Silva levelled the scores in the final exchanges, before Man City triumphed on penalties.
There is pressure on Rashford to perform this season, as a poor 2023-24 campaign saw the 26-year-old only manage eight goals in 43 appearances in all competitions.
However, Ten Hag is certain that the Red Devils academy product will become a regular goalscorer for the team once again this season.
Ten Hag insists Rashford "will score goals"
"I think he was several times in very good positions. I'm very pleased he is getting in those positions. Keep going, keep making those movements and the team will make those movements, he will score goals. He's experienced enough to deal with this and once he scores one, then the goals will come," Ten Hag told reporters.
After the Community Shield, the Man United boss also addressed his decision to leave Harry Amass out of the squad and instead select Lisandro Martinez at left-back.
Amass has been heavily involved in Man United's pre-season, and the 17-year-old was widely expected to start against Man City due to the absences of Luke Shaw and Tyrell Malacia.
A lack of full-back options led to Facundo Pellistri finishing match at right-back, but Ten Hag has stood by his decision not to name Amass in the squad for the Manchester derby.
Ten Hag defends surprise Amass omission
"I think we had some seniority there," Ten Hag said. "To start, I think that was the idea. We had a plan how to deal with it and I think also that went how we thought.
"I think all the full-backs, although not all were full-backs, like Licha, he did good as a full back. Diogo is the full-back and Facundo did well as the full back. We are pleased with those performances.
"You need squad depth, you need players who can play in multi-functional positions and when there is an emergency you have to have the option to play players to play in different positions.
"They (Martinez and Pellistri) are both capable, that is not their best positions but maybe it can grow into their best position for the team."
Man United, who will begin their 2024-25 Premier League campaign against Fulham on August 16, are expected to confirm the double arrival of Bayern Munich's defensive duo Matthijs de Ligt and Noussair Mazraoui on Monday.