The transfer window in England may now be closed, but that has not put an end to speculation about future signings at Manchester United.

The rumor mill has predictably gone into a frenzied overdrive following some inflammatory remarks by Cristiano Ronaldo at the weekend. The Portuguese forward failed to celebrate either of the two goals he scored in Real Madrid's 3-0 victory over Granada on Sunday and then made some intriguing comments regarding his future with the Spanish champions.

"I'm sad--when I don't celebrate goals it's because I'm not happy." Ronaldo said. "It's a professional thing. Real Madrid know why I'm not happy."

Ronaldo's words have sparked speculation that he could be set to exit the Bernabeu, with the Sun claiming that Manchester United have been put on alert by their former player's potential availability.

The Sun, who also report that Manchester City and Chelsea are interested in the player, have printed a quote from an alleged source who claims:

"Yes, Cristiano told president Florentino Perez he wants to leave the club."

According to the Daily Telegraph, however, Ronaldo's comments are merely a reflection of his desire to earn an improved contract offer from Real. With the expiration of a tax loophole for top foreign earners in Spain, Real will have to pay significantly more money in order to maintain Ronaldo's current wages. There is also a belief that Ronaldo's relationship with some of his team mates, particularly Marcelo, is not all it could be.

While a return to Old Trafford for Ronaldo still appears more than a little farfetched, Manchester United have also been linked to what could be a more realistic forward target. The Daily Mail claims that United are interested in bringing in Brazil striker Leandro Damiao in the January transfer window.

The Internacional star has long been pursued by Tottenham, while Liverpool were also linked to the 23-year-old last week. According to the Mail, though, United considered making a move earlier this year and intermediaries met his representatives to discuss a January move in Sao Paulo on Monday.

A move for Damiao midway through the season may makes sense as it wouldn't be complicated by the familiar problem of the player being cup-tied for the Champions League.

Having signed Robin van Persie last month, giving United four strikers often vying for one starting berth, a move for Damiao would represent a surprise. Certainly, if he were to arrive it would fuel further speculation about the future of the currently-injured Wayne Rooney.

There has also been further discussion about reported Manchester United target Liam Moore. The 19-year-old central defender has become a fixture for Championship side Leicester City this season after a loan spell at Bradford City during the first half of last term.

Metro now reports that Arsenal have joined United, Tottenham, Everton and Aston Villa in sending scouts to watch the England Under-19 international in action in recent weeks.

The story suggests that Leicester value the player at £5 million and are open to selling him in January.