The 31-year-old netted 253 goals in 559 appearances for the club while collecting trophies aplenty - achievements Mourinho believes someone like Lukaku will find hard to match, no matter his quality.
In fact, going by Mourinho's rationale - the total goals scored - it was actually much more hard. Opta tell us that if he scores against his old club Everton, he'll become the fourth-youngest player in Premier League history to hit the 90-goal mark.
"I think sometimes in this country the word "legend" comes too easily".
"I think we can achieve great things", said Ibrahimovic, whose team-mates host Everton on Sunday.
"He has nothing to prove, of course not".
If Manchester United have been dominant and consistent, unfortunately we would have to say the opposite about Everton.
A "worried" Ronald Koeman will, meanwhile, hold a meeting with Everton's squad where he will urge experienced players such as Rooney to drag them out of their rut.
Koeman has rightly said that it is not the right time for shedding frustration, because they can hardly do anything before the next transfer window kicks in. The Belgian has provided a focal point in attack, and he has scored four goals in four league games.
Ashley Williams is expected to return to the starting XI on Sunday but alongside Michael Keane and Phil Jagielka the lack of pace in front of Jordan Pickford is something Mourinho may look to expose. "That is an opportunity for others and the others are ready to get that opportunity and perform".
He captained his side in the Champions League match against FC Basel on Tuesday, but he was subbed off in the first half after suffering from a muscular problem.
Mourinho was also on hand to spout platitudes aplenty, making the frankly audacious claim that "Everton have lots of good players, they're a good team and it will be a very hard match for us".
The two meetings between both clubs last season ended with 1-1 draws.
Historically, it has been a classic fixture.
Manchester United are undefeated at home this season, notching three wins in three games across all competitions.
"He is a player who has adapted to the Premier League, with good friends already in this dressing room, with an easy integration in our group", he said.