He represented mainly Porto during his career, amassing Primeira Liga totals of 268 matches and 47 goals over 12 seasons and winning 11 major titles, including three national championships and the 2011 Europa League.

Born in Almada, Setúbal District and of Cape Verdean descent,[2] Varela was product of Sporting CP's youth system, being loaned to Casa Pia A.C. and Vitória F.C.

[8] Before the season was over, in March 2009, courtesy of his solid performances at Estrela, only relegated from the Primeira Liga off the field, Varela signed a five-year agreement with champions FC Porto on a free transfer, starting in July.

[10] In his first year he ranked second in overall goals in the squad, only behind Radamel Falcao; in March 2010, however, he broke his fibula in training, being lost for the remainder of the campaign[11] as the team finished third.

[19] Having arrived whilst still recovering from injury,[20] he made his official debut on 2 December, replacing Craig Gardner midway through the second half of a 1–2 home defeat to West Ham United.

[24] In the final two Serie A games of the campaign, his goals earned 2–2 draws against Hellas Verona FC and UC Sampdoria, though the team from the Stadio Ennio Tardini finished dead last.

[27] Having made only seven appearances for Porto during the season, Varela, who was by then the club's longest serving player, ended his seven-and-a-half-year link on 20 January 2017 by signing for Turkey's Kayserispor.

[28] He and fellow veteran Asamoah Gyan were told at the end of their contracts in June 2018 that they would only be retained if they signed performance-based deals, due to their injury record.

[36] Due to his Porto performances, Varela earned his first full cap for the Portugal national team on 3 March 2010, appearing in the second half of the 2–0 friendly win over China in a match played in Coimbra.