Ronaldo realised future greatness after Manchester United arrival

Cristiano Ronaldo says he discovered he belonged to a "world of stars" upon comparing himself to the rest of Manchester United's strong squad in 2003.

The future Real Madrid and Juventus forward rose to a prominence after moving to Old Trafford from Sporting CP as a skinny teenager.

Then a flashy winger, Ronaldo scored four goals from 29 appearances in his debut Premier League campaign.

Ryan Giggs, Paul Scholes and Ruud van Nistelrooy were among United's most prominent players at the time and Ronaldo quickly gained belief he too was destined to reach the top of the game.

"When I started playing for Manchester United at 18, 19, because I was as good as the players who were there I realised 'I'm close to achieving great things'," Ronaldo told Portuguese broadcaster TVI.

"Of course, I was a kid and I had a lot to learn – and I learned a lot from them – but I was in that world of stars.

"I saw that they were not doing anything that I couldn't do.

"There were better players than me: Giggs had more experience and was a better player than me at the time, Rio Ferdinand, Roy Keane, [Ole Gunnar] Solskjaer... but I felt that if I worked, with the talent I had, I could be the best player in the Premier League, for example."

Ronaldo spent six seasons at United, winning a first Ballon d'Or the before a €94million (£80m) transfer to Madrid in 2009.

The Portugal captain has since scooped European football's foremost individual honour a further four times.

Barcelona superstar and long-time rival Lionel Messi is the only other player to have claimed the Ballon d'Or on five occasions.

"I know that I am one of the best in my work and that I am in the history of football," Ronaldo said.

"It is no coincidence that only Messi and I have five. It is no accident. And I still feel motivated to try to win collective and individual prizes."

Ronaldo and Juventus commence their Serie A campaign away to Parma on Saturday.