The Portuguese star has won five Champions League titles in his career.
And it all started at United with Sir Alex Ferguson.
The 34-year-old won three Premier League titles, an FA Cup and a European honour at Old Trafford.
This has seen the forward judged to be one of the best players to play for the club.
But footage has emerged of Giggs, who made nearly 1,000 appearances for the Red Devils, making a big admission about Ronaldo.
In the clip, the current Wales manager is asked who the best player he has played with is.
“Ronaldo,” the 45-year-old said without hesitation.
Giggs’ claim comes as:
But the United legend had changed his mind after a moment of thought.
“He’s the best player I’ve played with,” Giggs added.
“But the best player I played with overall at United was Paul Scholes.”
The Englishman scored 155 goals in more than 700 appearances for the Red Devils.
And Giggs went on to explain his reason for choosing his fellow ‘Class of ’92’ graduate.
“Paul Scholes was clever,” the Welshman continued.
“He wasn’t that quick.
“But he knew where the ball was going to be or what he was going to do with it when it came to him.”
Giggs is not the only to have a controversial opinion on Ronaldo, though.
Ronaldo moved from Real Madrid to Juventus last summer for £89m.
He now has to get past Ajax, who knocked his old side out of the Champions League, if he wants a sixth title.