The Portuguese burst onto the scene after stepping out of a famed academy system in Lisbon.
It did not take long for his potential to be noted, with Sir Alex Ferguson taking him to Old Trafford in 2003.
Ronaldo has enjoyed a goal and trophy-laden career since then, with a standing cemented among the all-time greats.
He has put in an incredible amount of effort to reach that point, with an insatiable desire for continuous improvement having first been noted while still in his teens.
Tonito, who was on Sporting’s books as Ronaldo was breaking through, told Gazzetta dello Sport of the dedication shown by a modern day icon to being the best: “Cristiano was a kid, but he was just like the man he became: humble, ambitious, determined and professional beyond belief.
“During training, he'd turn heads among the veterans, and I'd say to him: 'Steady, don't overdo it...'
“I would also give him lifts [to and from training].
“But I'd have to wait an hour at the training ground, because he never wanted to leave.
“I'd bang on the window of the gym and say: 'Come on, Cris, it's time to stop - it's getting late!”
Those efforts have served Ronaldo well, as he is now considered to be one of the finest talents to have ever played the game.
He hopes to have “many more years” left in him, though, and there may be more moves to come.
Back in January, Ronaldo hinted to Record that he could take his career full circle and retrace his steps back to Sporting before hanging up his boots.
He said: “Will I go back to Sporting like Nani? In football you never know.
“Everyone in Turin welcomed me in a fantastic way. We're all feeling very good.
“I don't know when my career will end, but I’m fine and I want to keep going for many more years.”