Ronaldo is in the tail end of his career, but the Portuguese star is showing no signs of slowing down with Juventus or his national side.
Saha believes that given how much his former teammate achieved at United and how he is revered by fans at the club, a reunion would be a great way to turn around the team's fortunes.
He told Compare.Bet: "All I can say to you frankly that I appreciate Cristiano even more today seeing him play with Juventus, because the guy is way older than when I first met him and played with him. What he does right now as a football player; it is insane.
"The physicality that he has still got, that drive. Imagine the impact he would have on the forwards that we have right now. They would see the obsession that this guy has got and that would be a great example.
"He is more obsessed than anybody I have seen. Even van Nistelrooy was not in his league in the way that he is acting in front of goal. He wants every ball over the 90 minutes and it is a joy to see.
"His dedication is unbelievable so to see him back at United would be more than a dream, because I'm sure that he would have a massive impact. Maybe less goals, but it would be amazing."