One friendly match was all it took for Sir Alex Ferguson to realise that Cristiano Ronaldo was something special.
There was already considerable hype around the 'new Ronaldo' by the time Manchester United travelled to the Estádio José Alvalade but the Portuguese's performance that day made the rumours look small.
John O'Shea practically finished the game with his legs tied in a knot as Ronaldo ran the Red Devils' defence ragged. And when Ferguson swooped in for the winger just days later, he had unwittingly executed one of the greatest coups in football history.
Ronaldo would go onto spend six years at Old Trafford, scoring 118 goals, capturing three Premier League titles and lifting the Champions League trophy aloft.
Come 2009 and the 32-year-old moved to Real Madrid for a world-record fee in a move that has propelled him to legendary status. Three European Cups, 411 goals and four Ballon d'Or titles kind of legendary.
All that considered, it would be quite the thought to see Ronaldo back in the Premier League and turning out for United in their clash with Liverpool this weekend. It's hard to see any English football fan rejecting such a scenario.
That being said - believe it or not - that entire narrative could actually have revolved around Liverpool as opposed to the team that usurped their league title record with Ronaldo's help.
Gerard Houllier, who managed the Reds between 1998 and 2004, revealed in 2010 that he had actually spotted Ronaldo before Ferguson had ever seen him kick a ball.
The Frenchman explained: ‘I saw him in the Toulon Under-21 tournament and we went for him, but we had a wage scale and we weren’t paying the sort of salary he wanted.
"Then Manchester United played a friendly against Sporting Lisbon and all their boys said to Sir Alex Ferguson, “You have to sign him”. But I agreed with not breaking the wage structure. I thought it would cause problems in our dressing room.
"I know some of the signings were not as sharp as they could have been. Maybe we would have won the title with Ronaldo, but we had Harry Kewell, who was outstanding at the time and was very hungry but got a bad injury."
You can just feel the quotes: 'but we had a wage scale' and 'but we had Harry Kewell' irritating each and every Kopite - ouch.
Of course, the rose-tinted glasses of hindsight are all too convenient but it's not as if Houllier was even oblivious of Ronaldo's talent, he saw it with his very own eyes.
Yet another Fergie victory over Liverpool and perhaps his most significant.
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