The 36-year-old argued that instead of bringing the Portugal striker back to Old Trafford, the club should have invested in ‘young hungry players’.
That is despite the Real Madrid legend scoring three goals in his last three games, while he is also the club’s top scorer across all competitions.
Ole Gunnar Solskjaer brought Ronaldo back to the Theatre of Dreams last summer, with the Portuguese superstar winning the club’s September, October and March Player of the Month awards.
And while he may not be the same player of old, he has still managed to find the back of the net more often than not.
But even though the Red Devils desperately needed a proven goalscorer in the summer transfer window, Rooney has admitted that it hasn’t worked out.
Speaking to Sky Sports, Rooney also appeared to take aim at Ronaldo’s lack of pressing, as well as the club’s decision to re-sign a player well into his thirties.
Asked if it was the right move, he replied: “You’d have to say no at the minute.
“I think he’s scored goals, he’s scored important goals in the Champions League early on in the season, he obviously scored the hat-trick against Tottenham, but I think if you’re looking to the future of the club, you have to go with younger, hungry players to do the best and lift Manchester United over these next two or three years.
“Obviously Cristiano is getting on a bit, he certainly isn’t the player he was when he was in his 20s, and that happens, that’s football.
“He’s a goal threat but the rest of the game they need more, they need young hungry players.”
It is not the first time, and it will almost certainly not be the last time that Ronaldo’s return to Old Trafford will be criticised this season, with Jamie Carragher among those to voice their concern.
Writing in his monthly Telegraph column, Carragher admitted that he does not think it was ‘a smart investment’.
He wrote: “Cristiano Ronaldo’s invaluable contribution to Manchester United’s Premier League win over Brighton was another reminder of his unparalleled appetite for goals.
“But it does not change this reality: United made a mistake re-signing Ronaldo last summer. It will be a bigger one keeping him next season.”
“Given the cost of signing such a superstar as Ronaldo (an estimated £500,000 a week), it is not a smart investment.
“Let me repeat: I am talking about this stage of his career, not casting a critical glance and everything he has achieved.
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“How can I, or anyone, credibly criticise someone who has won five Champions League titles and scored over 800 goals?
“But if you sign Ronaldo right now, it is short-term recruitment expected to deliver instant success.
“United are way off the pace domestically and it would be a major surprise if they win the Champions League.
“That is why Ralf Rangnick is openly speaking about the need for United to sign another striker before next season.”