Sanches became the youngest player to score at Euro 2016 when he found the back of the net against Poland – taking the mantle from Turkish intentional Ozan Tufan.
Nani was quoted by Sky Sports as saying: “Renato would have been a great signing for Manchester United. I have no doubts.
“But he had a choice – and the choice he made was Bayern Munich.”
Nani does of course know all about United having won four Premier League titles and the Champions League during his time at the club.
The 18-year-old attacking midfielder is the youngest player at the European Championships and will play at Bayern Munich next season.
Bayern Munich completed a deal for the Portuguese intentional back in May for an initial fee of £27.5 million.
Sanches and Nani are both expected to feature for Portugal in the Euro 2016 semi-final against Wales next.
Nani is currently the joint top scorer for Portugal with two goals alongside Cristiano Ronaldo.
The experienced winger is expected to leave Fenerbahce after Euro 2016 with Valencia being his most likely destination.