Ahead of the Portuguese attacker's return to Old Trafford for the first time since departing in 2009, the Scot has claimed the Real Madrid star is an unrivalled talent
On Tuesday evening the Portuguese attacker will run out on the Old Trafford turf for the first time since making the £80 million switch to the Santiago Bernabeu back in 2009.
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And, when asked whether the 28-year-old has since established himself as the best player in the world, Sir Alex told ITV: "At this moment in time I think he is."
"Ronaldo's a special player, we know all about that.
"He's a mature man now. I think he'll get a great reception, but he's got a job to do - he plays for Real Madrid now - but we'll do our best."
The Scot also agreed with Jose Mourinho's declaration that the visitors will score at Old Trafford, adding: "I think they will. But so will we."