Manchester United Transfer News: Cristiano Ronaldo 'Unsettled,' Latest Rumours

Cristiano Ronaldo's vow of silence at Real Madrid has led to speculation suggesting he could head back to Manchester United.

This inevitable claim was reported by Jack Wilson of the Daily Star, who links the Portuguese icon to United after Madrid's 4-3 Champions League loss to Schalke on Tuesday night.

Pete Jenson of the MailOnline indicates there are "concerns" Ronaldo could be "unsettled" after he and his Madrid team-mates were booed off the Bernabeu pitch, despite progressing to the European quarter-finals with a 5-4 aggregate win.

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Ronaldo became the Champions League's all-time leading goalscorer with his two goals, but he spoke his last public words until the summer after the match, per Jenson: "I won't talk again until the end of the season."

Dermot Corrigan of ESPN FC offered a guess toward why Ronaldo has taken this decision:

Former Red Devils captain Roy Keane, who was part of the ITV punditry team for the match, suggested Ronaldo didn't seem right, reported by Anthony Hay of the MailOnline:

"

He (Ronaldo) looked frustrated tonight. His body language wasn’t great. I think he was frustrated with everything with the way he started the game and then with his team-mates because the guy is a winner but obviously he produced the goods.

"

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Links to a United return are never far away, particularly when you consider the tough time Ronaldo's former club are currently working through. Just two points clear in fourth and without a hope of landing silverware this season, Louis van Gaal's side could use some explosive attacking power to get their prospects back on track.

Ronaldo led United to every trophy worth winning between 2003 and 2009, developing into one of the world's best under former boss Sir Alex Ferguson. United have failed to replace the quality of either, a shortcoming that has seen the club's attacking identity diminished in recent times.

United built their success with players such as George Best, Ryan Giggs and Ronaldo bombing down the wings, scoring vital goals and epitomising the side's goalscoring prowess. Today's standard rests with wingers such as Nani, Antonio Valencia and Ashley Young, players who have all struggled for consistent quality during their tenures with the club.

Ronaldo would certainly lead United's best starting lineup, which was recently discussed by B/R UK's Sam Tighe:

In September 2014, Sky Sports' Guillem Balague suggested Ronaldo could head back to United in the future:

"

He has this idea, I think, that at Real Madrid he is doing a job and he is working, but he enjoyed himself almost like a kid at Manchester United. He dreams of going back to Manchester United and Manchester United have got all the finances in place to get him.

When will that be? It depends, of course, on a lot of things. It depends on Real Madrid and on Cristiano himself.

"

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However, just a month after this report, Madrid boss Carlo Ancelotti told The Sun (h/t Matt Morlidge of the Daily Mail) that Ronaldo is going nowhere: "Ronaldo will go to the end of his career at Real Madrid. I'm 100 percent certain he will be here next season not at Manchester United—100 percent."

United fans will always hope their legendary star has it in his heart to return. James Dickenson of the Express believes Van Gaal will be handed £150 million to improve his squad in the summer, so the funds are available to at least make an attempt at his signature.

He remains undroppable and a constant match-winner, however, meaning Madrid are unlikely to cash in on their most marketable star of all.