Ibrahimovic's first season in the Premier League has been cut short after picking up a knee ligament injury that will require surgery.
His absence will give Rashford an opportunity to play in his favourite position up front, but the 19-year-old is eager to see 'Ibra' extend his stay at Old Trafford because he has learnt so much from the Swede.
"You will see the benefits in years to come. What I have learnt from him is irreplaceable," Rashford said, according to ESPN FC.
"His influence, on the younger players especially, is fantastic. We want that to continue because he is making us into better players.
"Now, when I go to the left or right, I see it differently to how I pictured it last season.
"They are things I didn't have naturally inside me. I didn't feel uncomfortable in the wide role, but when something is different it takes a while to get used to it.
"For me, the development has been going great all the way through. Next season I think I will have come across most situations that are going to occur."