The 19-year-old England international believes his new role under the Portuguese coach has helped him become a far more rounded player, saying the profile of a forward in the game has evolved over the years.
"For me the development has been going great all the way through," Rashford told The Daily Telegraph.
"I didn't feel uncomfortable in the wide role, but when something is different it takes a while to get used to it.
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“You look at all the strikers in the world now, I can only think of two, three who are No 9s – (Tottenham Hotspur's Harry) Kane, (Bayern Munich's Robert) Lewandowski, (Barcelona's Luis) Suarez. The qualities a striker needs now are different to what they used to be.”
Rashford has made 45 appearances this season and will be in line to start at centre forward against Manchester City in the Premier League on Thursday after Ibrahimovic was ruled out for the rest of the season with a cruciate knee ligament injury.
The 35-year-old Swede, having enjoyed a successful career in the Netherlands, Italy, Spain and France before arriving at Old Trafford, has been a great role model for Rashford.
"His influence on the younger players, especially, is fantastic," added Rashford. "You will see the benefits in years to come. What I have learnt from him is irreplaceable."
United are fifth in the league, trailing fourth-placed City by one point in the race for a Champions league qualifying spot ahead of Thursday's crunch Manchester derby.
(Reporting by Hardik Vyas in Bengaluru; Editing by Ken Ferris)
