The Portugal international has won back-to-back Premier League titles with City, but says his greatest achievement came in Ligue 1.
"The title race with Liverpool last season was very tough, but in my short career, it was probably my second best achievement because winning the league with Monaco [in 2017] against Paris St-Germain was even bigger. The gap is huge and it only happens every 20 years. Last year was a special Premier League season but that year at Monaco was crazy.
"After Monaco lost 5-3 against Manchester City in the Champions League [last-16 first-leg match in February 2017], I did some interviews after the match, and Pep Guardiola and I crossed paths. He said congratulations on the game and that I was a very good player but it was only a quick chat.
"You could always see with the way Pep's teams played at Barcelona, Bayern Munich and now City. He was always a manager I wanted the opportunity to work with. When it came up, I could not say no.
"We had a WhatsApp group at Monaco at the time and the title was 'transfer market' for a few hours because we knew that Monaco playing in the Champions League was going to generate interest from other clubs."