In a sensational deal, Manchester United signed Ronaldo from Juventus towards the end of the transfer window, 12 years after he left the club in 2009.
Manchester United will be paying an initial fee of €15m over five years and Ronaldo has signed a two-year contract with an option of another year.
However, there are question marks over whether the 36-year-old can handle the Premier League despite him scoring 101 times in 134 appearances for Juventus.
And Parlour admits that he is baffled that the veteran forward is being doubted despite his obvious qualities and ability even in the twilight of his career.
He pointed out that Ronaldo remains a physical specimen despite his advancing years.
Parlour said on talkSPORT: “Ronaldo [can do everything].
“Left foot, right foot, headers and I have heard people doubting him maybe going into Manchester United.
“How can you doubt him?
“He is 36 years old but his medical would have been, he just took his shirt off and you passed it.”
Ronaldo scored his 110th and 111th goals for Portugal against Ireland on Wednesday night to become the highest ever goalscorer in international football.
