Ronaldo memorabilia at Sporting CP's museum
At age 16, Ronaldo was promoted from Sporting's youth team by first-team manager László Bölöni, who was impressed with his dribbling.[26] He subsequently became the first player to play for the club's under-16, under-17, and under-18 teams, the B team, and the first team, all within one season.[21] A year later, on 7 October 2002, Ronaldo made his debut in the Primeira Liga, against Moreirense, and scored two goals in their 3–0 win.[27] Over the course of the 2002–03 season, his representatives suggested the player to Liverpool manager Gérard Houllier and Barcelona president Joan Laporta.[28][29] Manager Arsène Wenger, who was interested in signing the winger, met with him at Arsenal's grounds in November to discuss a possible transfer.[30]

Ronaldo came to the attention of Manchester United manager Alex Ferguson in August 2003, when Sporting defeated United 3–1 at the inauguration of the Estádio José Alvalade in Lisbon. His performance impressed the Manchester United players, who urged Ferguson to sign him.[31] Ferguson himself considered the 18-year-old "one of the most exciting young players" he had ever seen.[32][33] A decade after his departure from the club, in April 2013, Sporting honoured Ronaldo by selecting him to become their 100,000th member.[34]