Wayne Rooney's recent appearance on Sky Sports' Monday Night Football has brought his relationship with fellow Manchester United legend Cristiano Ronaldo firmly into the spotlight.

While covering Crystal Palace's 3-0 victory over Arsenal earlier this week, Rooney was asked whether Ronaldo's second stint at Old Trafford had been a success.

"You'd have to say no at the minute," replied United's record goalscorer.

"I think he's scored goals, he's scored important goals in the Champions League early on in the season, he 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."

MANCHESTER, UNITED KINGDOM - SEPTEMBER 27: Wayne Rooney of Manchester United celebrates scoring his team's second goal with team mate Cristiano Ronaldo (R) during the Barclays Premier League match between Manchester United and Bolton Wanderers at Old Trafford on September 27, 2008 in Manchester, England. (Photo by Clive Brunskill/Getty Images)

Ronaldo was quick to snap back at Rooney on social media, implying that the England striker - who retired last year - was "jealous".

The Derby boss has since laughed off that response, admitting that pretty much player, bar Lionel Messi, is envious of the five-time Ballon d'Or winner.

The Rooney and Ronaldo relationship dates back close to two decades to their early days at the 'Theatre of Dreams', where both thrived under the leadership of Sir Alex Ferguson.

MANCHESTER, UNITED KINGDOM - MAY 15: Sir Alex Ferguson the manager of Manchester United talks with Cristiano Ronaldo ahead of the UEFA Champions League Final during the Manchester United media day held at the Carrington Training Complex on May 15, 2008 in Manchester, England. (Photo by Alex Livesey/Getty Images)

While Ronaldo might be several leagues above Rooney in terms of superstar status today, the scouser once revealed that he frequently had to protect his Portuguese colleague from Sir Alex's infamous hairdryer treatment during his first few years at Old Trafford.

In modern times, Ronaldo has adapted his game to become a predatory goal poacher. However, when he first burst on to the scene, the now 37-year-old was a flashy winger who combined electric pace with a variety of tricks and skills.

At times, though, Ronaldo's attempts at dazzling the crowd did not go down well with Ferguson, especially if United weren't in control of the game at the time.

MANCHESTER, ENGLAND - AUGUST 9: Cristiano Ronaldo of Manchester United during the Champions League third qualifying round, first leg match between Manchester United and Debreceni VSC at Old Trafford on August 9, 2005 in Manchester, England. (Photo by Clive Brunskill/Getty Images)

A master at man-management, Sir Alex realised that giving Ronaldo both barrels would probably do more harm than good to the young player's confidence.

Whenever Ferguson had an issue with Ronaldo or his countryman Nani, then, he would instead spew all of his criticisms in Rooney's direction - and get his message across in that fashion.

We actually had [an argument] almost every game, at half-time," Rooney revealed in an interview earlier this year, per The Mirror. "It's just he'd see the way the game was going, he'd have a go at me.

Can you name these UEFA Champions League final stadiums?

"If [Luis] Nani or Cristiano were dribbling along and losing the ball, he'd come in at half-time and have a go at me for dribbling. And he knew that would get me fired up.

"I'm looking, thinking, 'You joking here? I've got these two dribbling constantly, losing the ball and you're having a go at me?' and then I'd have a go back at him.

"He knew that it would get a reaction out of me and it was his way of saying to those two: 'Stop dribbling with the ball'. Because if he said it to these two, there'd probably be tears."

MANCHESTER, UNITED KINGDOM - SEPTEMBER 25: Alex Ferguson the manager of Manchester United talks with Wayne Rooney during a Manchester United training session held at the Carrington Training Complex on September 25, 2006 in Manchester, England. (Photo by Alex Livesey/Getty Images)

Rooney continued: "He enjoyed it, he knew what he was doing. He knew exactly what he was doing, he enjoyed us having a go back because he knew that would light the rest of the players up. He knew I played on the edge, especially at that time and it got me going."

Ronaldo, of course, still plays with an abundance of confidence today. Who knows, though, whether that self-assuredness might have taken a real beating had Rooney not stood up and willingly taken the brunt of Ferguson's ire during their time together at United.

Rooney may not have won a Ballon d'Or while at Old Trafford like Ronaldo did in 2008, but he's still scored more goals for the club than anyone else (253 to Ronaldo's 136 overall).

Both are true icons of the 'Theatre of Dreams'.

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