Rashford, 18, made a stunning breakthrough last season, scoring eight goals in his first 18 United appearances and earning a berth in England's Euro 2016 squad.
Ibrahimovic's arrival has cost Rashford his first-team place, but he made a big impact off the bench in Saturday's 2-1 loss to Manchester City and his Swedish team-mate believes the future will be his.
“First of all, he's 18, he's still young. He has a lot of time,” Ibrahimovic told MUTV. “I think the way you have to approach a player like that, where everyone is talking about the talent and what he's able to do and what kind of potential he has, is to remember he still has a lot of time.
“It's not like he needs to take over the world today. The club knows that, the coach knows that and the team knows that. We know his quality and what he's able to do. What the world is seeing now, we already know because we see it every day.”
“There is no need to rush to push him and put a lot of pressure on him because that can have the opposite effect. Time by time, he will take over everything. It's about having patience.”