By Graham Ruthven (@grahamruthven)  It’s something of a shame that statistics aren’t kept on how many times Cristiano Ronaldo shrugs his shoulders, puffs out his cheeks or waves his arms in protest. If they were it would show the Portuguese winger showed some form of petulant frustration more often that he touched the ball in Real Madrid’s crushing Clasico defeat to Barcelona. Indeed, his performance on Saturday certainly won’t go down in the grand catalogue of Ronaldo’s best, continuing something of a trend for the increasingly vexed Real Madrid number seven. Signs of his natural decline, having passed his 30th birthday, are all too apparent and becoming more evident with every passing game.  And so the question has been asked with pressing pertinence, perhaps for the first time: should Real Madrid cast off Ronaldo - their all-time top goalscorer, poster-boy and embodiment of the Galacticos’ second coming? The three-times Ballon d’Or appears to have lost some of the drive that has made him such a force of nature over the past decade, facing scrutiny from those who not so long ago hailed him the best of his generation.  It could be that, like so many who enjoy prolonged success at the very top, Ronaldo needs a fresh challenge to reboot his motivation - and there are no shortages of clubs willing to offer him as much. Should Real Madrid decide to sell, they won’t have an issue in finding a buyer. Manchester United, for one, would offer Ronaldo the chance of a Premier League return. The Old Trafford club, and their fans, long for the homecoming of their favourite Portuguese son, with Louis Van Gaal openly confessing his hope that such a move will one day come to pass. "We are looking at all players, not just Ronaldo. But these players are mostly ungettable,” the Dutchman said after Saturday’s win over Watford. "With Ronaldo, let's wait and hope. Ronaldo plays on the wings and he is fast and scores goals. There is no trainer in the world that doesn't like him." United would have competition for Ronaldo’s signature, though. According to reports this week, Paris Saint-Germain president Nasser Al-Khelaifi visited the Spanish capital last Thursday, holding court with super agent Jorge Mendes. Of course, Al-Khelaifi likely meets with such higher powered footballing figures regularly - with Angel Di Maria on the books of both PSG and Mendes - but the future destination of Ronaldo will have surely cropped up in conversation. And the French capital might provide Ronaldo with a more appealing destination, giving him a more suitable final step for his elite career. There he would play his part in the coming of age of a burgeoning super-club, taking in another glitzy and glamorous European city. Besides, Ronaldo isn’t the most natural of fits for Man Utd - and more specifically Van Gaal’s disciplined, well-drilled system. Nonetheless, the Old Trafford club are in need of a spark and a renowned face to sell jerseys - and in that sense the number seven certainly fulfils a brief. 

What’s more, there are some instances in football when pragmatism should be cast aside. The impact of some players cannot be quantified, providing a lift that cannot be fully explained. For Man Utd, Ronaldo would be that player, just like Cesc Fabregas would have been for Arsenal or Didier Drogba was for Chelsea.  At 30 years old, Ronaldo would come attached with little or no sell-on value, meaning at least £60 million (the reported fee demanded by Real Madrid) would have to be almost completely written off by any potential buyer. Regardless, the temptation might be too strong for many of Europe’s best teams. Even if Ronaldo has indeed passed his peak he is certainly still good enough to command a place at any other elite side.  If indeed Ronaldo is to leave Real Madrid - the club where he became a true legend of the game - he must decide what exactly he wants from this juncture on. At PSG he could take in yet another country, captivating yet another super-club. But the lure of Old Trafford - where he is still cherished most - is strong, and Ronaldo could be forgiven for once taking the easy option.