S.L. Benfica 2015, Benfica reported to have 246,401 members; however, after a scheduled renumbering by the club in August 2015, the number decreased to 156,916. In April 2017, Benfica reported they had a total of 184,264 members by 31 December 2016. Benfica has rivalries with Sporting CP and FC Porto, with whom it forms the "Big Three": Portugal's most decorated clubs. None of them have been relegated from the Portuguese league since its establishment in 1934. As Lisbon-based clubs, Benfica and Sporting have shared a rivalry for over a century; it all started in 1907 when eight prominent Benfica players defected to
FC Porto in international football competitions name="1980/81"></ref><ref name="1982/83"></ref> In between, the club sailed into the 1981–82 Cup Winners' Cup quarter-finals, where they were beaten by the eventual runners-up Standard Liège.<ref name="1981/82"></ref> Porto lost the 1983 Portuguese Cup final to league champions Benfica, which allowed their participation in the 1983–84 Cup Winners' Cup as losing cup finalists. They eliminated Dinamo Zagreb, Rangers, and Shakhtar Donetsk to reach their first European semi-final.<ref name="1983/84"></ref> The competition draw paired Porto with the holders Aberdeen, managed by Alex Ferguson. Taking a 1–0 lead to Pittodrie, Porto resisted to the attacking pressure of their opponents. In the 76th minute, Vermelhinho scored the