Brought to Old Trafford in 2007 for more money than it took to secure the services of Cristiano Ronaldo from the same Sporting Lisbon source, apart from a few sporadic performances and a couple of eye-catching goals, Nani has failed to convince.
The critical voices have become louder in more recent times, to the point of ridicule by some, and it would have been no surprise if Ferguson had decided to sell the Portugal wide-man during last month's transfer window.
Instead, Ferguson remained faithful to the 23-year-old. His reward has been staggering.
First, Nani ran Hull ragged at Old Trafford. Then he provided the impetus for United's Carling Cup semi-final triumph over Manchester City.
Yet even those performances were eclipsed by a mesmeric display against Arsenal last weekend that will stand comparison with any individual performance in the Premier League this season.
The piece of skill that led to the visitors' opener would have brought admiring gasps from Ronaldo himself, while he was central to Wayne Rooney's effort shortly afterwards which was very similar to the goal United scored at the other end of the same stadium last season to seal a place in the Champions League final.
While it would be tempting to simply claim Nani has stepped out of Ronaldo's shadow, Ferguson does not believe that is the case.
The Scot does think the adjustment to life at Old Trafford, that has been too much for some top quality players - Diego Forlan is a prime example - has just taken a long time for one of United's quiet men.
"I don't think he was overshadowed by Ronaldo. It was just a question of maturity," said Ferguson.
"Nani was young when he came here and he is quite a shy boy.
"Some players can adjust to coming to another country and joining Manchester United very easily.
"In the past, others have taken time. Patrice Evra and Nemanja Vidic came to us in the January but it was nearly a year before they hit the form we see in them now. Nani is much the same."
A recent spell on the sidelines may have caused the penny to drop.
If Nani had seen United labour in attack, he would have known pace, getting defenders onto the back foot and early crosses have been conspicuous by their absence.
He was capable of all three aspects. He just had not delivered them.
"Maybe watching has been the best thing for him," said Ferguson.
"He has shown maturity in his last three games, which we always felt was the key.
"The assets have always been there. What we have looked for is consistency.
"We are pleased for him because when he is in that kind of form he is a great addition for us and everyone saw the influence he had on the game on Sunday."
Do you think Nani will maintain his form? Have your say.
Source: Manchester Evening News