It was simmering before Christmas, but now things are threatening to boil over in Madrid.
Ronaldo spoke openly last season of receiving photos from Manchester City's owners of luxury cars full of cash when they came calling. But while City will be front and centre should Ronaldo push for a move, a return to United is the more likely - particularly with his agent, the high-profile Jorge Mendes, now so close to the decision-makers at Old Trafford.
No other agent enjoys the relationship Mendes has with United directors. He now has delivered Cristiano Ronaldo, Nani, Anderson, David de Gea and Bebe to Old Trafford in the past eight years and is also driving the end of season deal for Benfica winger Nicolas Gaitan.
Mendes, who also represents Real coach Jose Mourinho, is close to Ronaldo and will know the former United star will be hurting over his fractured relationship with fans.
His friends are also upset with the treatment Real's boo-boys are dishing out. One spoke to AS only last week, declaring: "The guy has feelings and was hurt that day (the El Clasico) when he left the stadium. He could not understand that the Bernabeu were abusing him for missing a pass or criticising him against Barca saying that he always fails when playing them."
It was after that defeat to Barcelona that Ronaldo began considering his situation at Madrid. He bunkered down at home the following Sunday, with just close family and friends, shocked by the abuse coming from his own supporters. As that same confidant said last week, those closest to Ronaldo also still regularly visit Old Trafford and report back on the Stretford End singing his name.
The abuse from the stands has continued and it isn't just the fans who have turned on Ronaldo. The club's honorary president, Alfredo di Stefano, gave the Portuguese zero support when asked about the jeers.
"The public are paying and are always right. If the public asks the player to maximize his efforts with goals, he should not question it," snapped the Real legend.
Just as he knows the support he still has from United fans, Ronaldo will also be well aware that Sir Bobby Charlton or Bryan Robson would never have left him high and dry given similar circumstances.
But if the emotions of being turned on by his own will be hurting Ronaldo, the Spanish government's scrapping of the David Beckham will also be weighing heavily.
Last year the David Beckham loophole, which allowed elite foreign workers — including professional sportsmen — to pay 24 per cent tax, half the top rate in Spain, was ripped up.
It's now just broke that La Liga's high earners will pay 54 per cent of their earnings to the taxman, which will prove a massive hit to Ronaldo and his R9 empire in Spain. While he's on a massive €12 million-a-year to 2015 at Real, such a n unexpected change is sure to shake up 'Team Ronaldo'.
Scholes' return has eased the tension, but United fans have flooded the talkback channels demanding why they failed to sign Wesley Sneijder from Inter Milan in the summer when all parties seemed happy to do the deal.
Could it be that the Glazers and Sir Alex Ferguson are keeping their powder dry for the summer return of Ronaldo? That money which would have gone towards signing Sneijder could now be used to bring back the one player Fergie has spoken openly about re-signing.
And with the club 's Stock Exchange float slated for later this year, what better way to attract investors than the return of Ronaldo and all the projected revenue he will bring?
It all seems to be coming together, the stars are aligning for what could be the greatest deal in the game's history.
Only yesterday, Ronaldo said in a Lisbon interview: "The Premier League and Spanish Liga are the two best leagues, but I'll be very honest. The English league is more competitive. The Spanish is competitive, but not as much as the Premier."
Pining for 'home'? As Fergie would say: "I can't believe it. I can't believe it. Football. Bloody hell."