A win for City in Sunday's derby will surely all but seal the title, though Nani does not consider them stronger than United.
Manchester United are 14 points behind rivals City in the Premier League, but Nani believes with Bruno Fernandes that gap could disappear.
Manchester United menjadi "sekolah" terbaik dalam kehidupan Nani selepas dia belajar bagaimana untuk bekerja di bawah Alex Ferguson tetapi ia bukan jalan yang mudah buat bekas bintang Portugal itu.
Marcus Rashford and Anthony Martial can play in the same Man Utd team but both players have improvements to make, says Nani.
Nani feels Manchester United look more like a team now but stressed Bruno Fernandes' arrival would have been tough for Paul Pogba.
Nani's Manchester United career was not always straightforward, and he puts that partly down to taking longer to adjust to Alex Ferguson.
Orlando City and Philadelphia Union won through to the quarter-finals on Saturday.
A draw was enough for Orlando City to win their group ahead of Philadelphia Union on Monday.
Orlando City overcame Inter Miami as MLS returned amid the coronavirus pandemic.
Nani has spent much of his career playing alongside Cristiano Ronaldo, and he believes the Juventus star may end up in MLS.