That is the opinion of former United goalkeeper Peter Schmeichel.
The Dane was in Monaco to witness the Champions League draw on behalf of Manchester United, who were drawn against BSC Young Boys, Valencia and top seeds Juventus.
The draw means Ronaldo will return to Old Trafford for only the second time since leaving in 2009.
His last visit was in 2013, when Real Madrid – then managed by Jose Mourinho – defeated United 3-2 on aggregate, thanks in large to Ronaldo goals in both legs.
Juventus are second favourites with the bookies to become European champions next June, but that stern challenge is something Schmeichel spoke of positively.
“You want to be in a group that’s exciting. You want to be in a group that produces some great TV matches also,” said Schmeichel.
“That’s kind of the big bonus, that we get Cristiano back to Old Trafford.
“I think the crowd at Old Trafford will be very, very happy to see him back.
“Of course last time he was there it wasn’t too great for Manchester United.”
Juventus have won the Scudetto for seven successive seasons, but lost in the Champions League final in two of the last four campaigns.
Schmeichel continued: “Playing against Juventus, they are probably the hardest team in Europe at the moment, because of this signing [Ronaldo].
“Everyone is looking at them as rebuilding the whole Italian club football scene again.
“It’s a massive signing for them and the expectation comes with having signed him.
“I think it’s going to be really a difficult game. There’s no doubt about that.”