That is why the revelation from Spain, that he is ready to quit Real Madrid after eight years against the ugly backdrop of a £13million tax evasion probe, has put Europe’s top clubs on high alert.
Not least Manchester United, whom he left in 2009 for a then world record fee of £80m, whose executive vice-chairman Ed Woodward has made no secret of his enduring regard for their former star player.
But with a fee likely to be in excess of £100m, despite his age, and a weekly wage of £365,000, even United fans who still idolise Ronaldo would surely question the wisdom of such an exorbitant financial outlay on a player who is approaching the twilight of his glittering career.
For United, the key question is whether Jose Mourinho feels Ronaldo, who he worked with during his three-year spell at the Bernabeu and with whom he endured a tense relationship at times, would fit his vision for the team going forward if he became available, or whether he would see it as a regressive step.
Although Ronaldo’s two-goal match-winning display in Real’s 4-1 Champions League final win over Juventus in Cardiff two weeks ago showed he remains the man for the big occasion, whether he could sustain it over a season in the relentless arena of the Premier League at 32 remains to be seen.
Statistics show Ronaldo played significantly fewer minutes last season than the previous campaign and, as he gets older, his game-time will need to be rationed to bring out the best in him, something Mourinho is reluctant to do with his players.
United are also pushing ahead with a £65m move for Real striker Alvaro Morata and there is no suggestion they would pull the plug on that deal on the off-chance Ronaldo may be available.
Moreover, Woodward and United have been here twice before, with Ronaldo flirting with a return to them by agitating for a move, only to end up signing lucrative new deals with Real.
Back in 2013, newly-appointed United boss David Moyes was convinced he was going to land Ronaldo or Gareth Bale. In the end, Ronaldo signed a three-year contract extension and Bale snubbed United’s desperate last-ditch £100m offer to join Real from Tottenham for £85m.
A cynical view would be Ronaldo’s camp have made it known he is unhappy because they want to draw another improved deal. But having signed a new five-year deal last November, keeping him at Real until 2021, the motive behind the leaking of his supposed disillusionment is unlikely to be that.
If Ronaldo is serious about leaving Real, the most likely destination for him is France or Germany, with Paris St Germain and Bayern Munich among the clubs ready to take advantage of his perceived disenchantment with life in Spain.
Ronaldo is said to be outraged at the decision by the Spanish authorities to charge him with tax evasion and feels victimised, according to Portuguese newspaper A Bola, which broke the story, branding as “irreversible” his decision to leave Real this summer.
Spanish newspaper Marca, widely accepted as being Real’s mouthpiece, later ratified the story, giving it a legitimacy that sent Europe’s top clubs into a frenzy over Ronaldo’s potential availability.
For now though, Europe’s top clubs must watch and wait, with a Madrid judge to rule within the next fortnight if the case should proceed to court. If so, Ronaldo will have 30 days to plead guilty and pay the requisite fine, or fight the charge and risk a heftier punishment.
Whatever the outcome, Ronaldo may be about to spark the transfer scramble of the summer, and send some United fans into a frenzy over a potential homecoming for their prodigal son, whose iconic No.7 shirt remains vacant.