Portuguese winger completed a thrilling United comeback but Ferguson plays down impact the result will have on the Premier League title race
"You see the form of Nani in preseason and today - he will start the season," Ferguson said. "He had a fantastic season last year. He was unfortunate that Valencia came in at a time when we needed a bit of freshness and a boost to the squad.
The Portuguese winger sealed the win at Wembley as he rolled home a last-gasp strike to complete a remarkable comeback from the Premier League champions after they had found themselves 2-0 down at the break.
Nani lost his place in the United starting XI towards the end of last season, raising some questions over his future at the club, but his manager was delighted to see him put City to the sword.
"He was only in [Cristiano] Ronaldo's shadow simply because he's Portuguese," said Ferguson. "That's the only link I could see between them. Some players take longer to mature than others. Ronaldo was different; he was an incredible footballer and matured immediately."
Nani's two goals, the first the finishing touch on a wonderful team move, followed Chris Smalling's 52nd minute strike as United fought back having trailed 2-0 at the break following goals from Joleon Lescott and Edin Dzeko.
Ferguson was keen to play down the psychological impact of United's win ahead of the start of the Premier League season but the Scot is satisfied with his young squad.
Danny Welbeck and Tom Cleverley, who spent last season on loan at Sunderland and Wigan respectively, caught the eye with impressive displays as United played with too much pace and precision for their city rivals.
"You can never be confident in the Premier League, it's such a difficult league," Ferguson explained. "Six teams could be challenging for the title and it will be a difficult season for us.
"I thought it was a great performance. For us, I think it just confirms what I thought about the squad.
"People have been saying that we're not the best United squad and things like that, but you've got to remember we have a lot of young players who will improve," he said. "We've brought Cleverley and Welbeck back from loans and these boys will improve."