Should Man United let Cristiano Ronaldo go for nothing now that he's a bit-part player at Old Trafford?

Could Man United swap Ronaldo for Napoli's Osimhen? (1:32)

Gab Marcotti and Julien Laurens discuss rumours that Cristiano Ronaldo is on the way to Napoli with striker Victor Osimhen possibly heading in the other direction. (1:32)

Life has come full circle for Cristiano Ronaldo at Manchester United, and he has now become a handbrake on the team's prospects of a successful future. It is time for United to let him go because the positive dividend on the pitch will, sooner or later, outweigh the financial cost of allowing him to leave Old Trafford for free this week.

Ronaldo's goals last season -- 24 in 38 appearances -- counted for little as United finished in sixth position in the Premier League and failed to win a trophy, but a bad season would probably have been much worse without the 37-year-old's contributions during a campaign that saw the team play under three managers and lurch from one crisis to another.

Yet football moves quickly, and as he approaches the first anniversary of his return to United from Juventus, Ronaldo has become yesterday's man.

The debate as to whether he was United's saviour last season, or the lightning rod for everything that went wrong, will rage on well beyond his second spell at the club. However, just four games into Erik ten Hag's reign as manager, it is clear that Ronaldo is now a bit-part player with no obvious role beyond that of a malcontent on the substitutes' bench.

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United have yet to prove they can live without Ronaldo's goals -- with Marcus Rashford, Jadon Sancho, Anthony Elanga and Anthony Martial still to show prolonged consistency up front. The €95 million signing of Antony from Ajax this week would help boost Ten Hag's options, but nonetheless, Ronaldo remains the only forward in the squad who can genuinely be described as a regular goal scorer.

There is a bigger picture that Ten Hag and United must now survey, and it cannot include Ronaldo and his goals. Back in 2006, then-United manager Sir Alex Ferguson made the bold decision to offload striker Ruud van Nistelrooy to Real Madrid, despite the Netherlands international delivering incredible consistency with 150 goals in 219 appearances for the club.

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It was a controversial move by Ferguson, but he would later reveal that he sanctioned Van Nistelrooy's exit because the player had become a brooding presence in the dressing room and was, in particular, stifling the development of a young teammate: Ronaldo.

"Ruud had started to mouth off all the time to [coach] Carlos Queiroz about Ronaldo," Ferguson wrote in his autobiography. "There were a few altercations all the way through his final season with us, but it was mainly Van Nistelrooy on Ronaldo."

Sixteen years on, there are similarities between Van Nistelrooy's departure and the situation United now face with Ronaldo. While there are no question marks over Ronaldo's professionalism and fitness, sources have told ESPN over a period of months that he has become a divisive figure within the squad. His demand for the highest standards on the training pitch should not be criticised, but sources have said that Ronaldo has been unable to accept that the United side he rejoined was a world apart from the one he left, both in terms of the calibre of the squad and the personalities within it.

Could Manchester United pay Cristiano Ronaldo to leave the club?

Gab Marcotti and Rob Dawson update on Cristiano Ronaldo's future after he was left on the bench for Man United's win vs. Liverpool.

In short, he expects the likes of Harry Maguire and Rashford to perform like Rio Ferdinand and Wayne Rooney and makes no allowances for their obvious shortcomings. When Ronaldo's desire to leave United became public in July, a source told ESPN that the news was greeted with joy by the majority of his teammates and that Ronaldo had become a "pain in the a---."

By missing the team's preseason tour of Thailand and Australia due to "personal reasons," Ronaldo was on the other side of the world as Ten Hag got to work with his new squad, attempting to forge a sense of unity that had been absent last season. As soon as Ronaldo returned to action, he angered his new manager by leaving Old Trafford at half-time of a preseason friendly against Rayo Vallecano.

Then came the woeful performance during a 4-0 defeat at Brentford, when Ronaldo was as culpable as the rest of his teammates for the loss. It was his only start under Ten Hag -- he played the full 90 minutes -- and has so far registered just 153 minutes, and no goals, in four games this season.

Having been greeted as a returning hero just 12 months ago, Ronaldo is now a source of friction in the dressing room and is failing to offer his new manager a positive football reason to select him in the starting XI. So why is he still at Old Trafford?

Primarily, United have simply been unable to find a club to take him. While the public position has been that Ronaldo is not available for transfer, sources have told ESPN that efforts have been made to find a club and that a move away from the Premier League would suit both parties. Yet with a year to run on a contract worth £500,000 a week, the lack of interest in a player who will be 38 in February is unsurprising, though Napoli and his former side Sporting CP are the latest to be linked with a possible loan move.

If Ronaldo was a less expensive proposition, clubs would undoubtedly emerge to sign him, so United now have a big decision to make.

In recent years, Arsenal took a financial hit by cancelling the contracts of Mesut Ozil and Pierre-Emerick Aubameyang -- along with a host of others -- in order to accelerate Mikel Arteta's rebuilding job at the Emirates, and with the Gunners now sitting at the top of the Premier League with an exciting young team, those decisions are beginning to pay off.

By coming to an agreement with Ronaldo, United would be giving Ten Hag the same opportunity to clear the air and push forward with his own agenda. The alternative would be keeping him until the end of his contract and hope that the problems will go away, but that is likely to be an even more expensive gamble.

From a football perspective, there is only one decision United can make.