Rashford hit 30 goals for United last season, but has scored just once during their woeful start to the campaign.
United boss Ten Hag believes one of the reasons for the England star's poor goal return is that the team as a whole are under-performing.
The troubled club have lost six of their 10 games in all competitions this season, falling well off the pace in the Premier League and slumping to the bottom of their Champions League group.
Ten Hag spoke about Rashford's form on Friday, on the eve of his side's home match against Brentford.
"That is, of course, the team and him," he said. "It is both, so I am sure that you are always not at the same levels.
"Of course, everyone knows his qualities but also the opposition knows the qualities.
"We have seen in the last (few) weeks that he is coming in the good positions, now he is struggling, but this will pass because everyone knows his qualities."
Ten Hag said one goal could boost Rashford's confidence and spark a scoring spree.
"It will come and he is so experienced, he knows that as well," said the Dutchman.
"When he is doing the right things and the team is doing the right things, that momentum will come and he will be on fire."
Rocked by their shock home defeat against Galatasaray in the Champions League on Tuesday, Ten Hag said his faltering team are struggling to find consistency.
"In big parts of the game, I would say, we do a lot of things right. But then we have moments when we are struggling and in such moments, we can't survive," he said.
"In those moments you have to do the right things, so be consistent and do your job, be consistent in the communication because when you do that, you keep the right organisation."
