In the off-season, Sven-Göran Eriksson left for Roma and Benfica hired Tomislav Ivic. Major departures included Fernando Chalana and Glenn Strömberg. To counter, the club added Jorge Silva, Wando and Adelino Nunes. Even before the end of the season, Ivic resigned and Benfica was forced to replace him in August. The selected was Pál Csernai.
Benfica never performed as expected and even suffered their longest ever win-less period in the Primeira Divisão. In the end, the team ended in third place, 12 points from first place, and lost the Supertaça Cândido de Oliveira. Still, it was not a trophy-less season as Benfica conquered their 19th Taça de Portugal in a 3–1 win against Porto.
The league campaign started in the best of ways, with two wins,[18] but on match-day 3, Benfica lost in the Clássico with Porto.[19] In October, Benfica began their European Cup campaign with Crvena Zvezda, defeating them on aggregate.[19] In the second round, Benfica met Liverpool and were eliminated.[20] Now fully focused on the league campaign, Benfica lost in the Lisbon derby in late December and got delayed in the battle to retain his league title.[20] There were now 6 points shy of leaders Porto.[20] On 20 January, Benfica drew with Braga on match-day 17 and started their biggest ever win-less period in the Primeira Divisão.[21] They would spend two and half months without winning in the league, with six draws and one loss.[21] Despite that, a Taça de Portugal campaign involving only second tier teams allowed the team to progress through the rounds with ease.[21][22][23]
The team eventually resettled and won all league matches in April.[24] In the Supertaça Cândido de Oliveira, a one-nil win for both Benfica and Porto forced a replay of the competition.[21] In early May, John Mortimore was confirmed as new manager, with Csernai still in charge for another month.[24] Before the end of May, Benfica lost away in the first leg of the Supertaça to Porto, but won the Lisbon derby with Sporting by 3–1, reducing the distance between them.[24] In June, Benfica lost again in the Supertaça, losing the competition and finished the league in third place, 12 points behind Porto and five from Sporting.[25][26] The season finished with the Taça de Portugal final against Porto, with Benfica winning 3–1.[27] It was their 19th Taça de Portugal win in 25 Finals, their seventh in eight against Porto.[27] After the win, Manuel Bento sent a jab to Csernai: "It was not Csernai who made the line up, that's why we won. It was Carlos Manuel and Minervino Pietra who opened his eyes."[21][23]
The squad for the season consisted of the players listed in the tables below, as well as staff member Pál Csernai (manager), Toni (assistant manager), Eusébio assistant manager), Júlio Borges (Director of Football), Amilcar Miranda (Doctor).[39]
Note 1: Note: Flags indicate national team as defined under FIFA eligibility rules. Players may hold more than one non-FIFA nationality.
Note 2: Players with squad numbers marked ‡ joined the club during the 1984-85 season via transfer, with more details in the following section.
^ abc"Chalana vale 300 mil" [Chalana is worth 300k]. Diário de Lisboa (in Portuguese). No. 21501. 7 July 1984. p. 15. Retrieved 15 March 2017.
^ ab"Benfica recupera" [Benfica recovers]. Diário de Lisboa (in Portuguese). No. 21427. 7 April 1984. p. 22. Retrieved 14 March 2017.
^ ab"Benfica recrutou Nunes" [Benfica signed Nunes]. Diário de Lisboa (in Portuguese). No. 21453. 10 May 1984. p. 14. Retrieved 14 March 2017.
^ ab"Mais mudanças" [More changes]. Diario de Lisboa (in Portuguese). No. 21464. 23 May 1984. p. 19. Retrieved 14 March 2017.
^"Nilsson: apartamento em Olaias" [Nilsson: Apartment in Olaias]. Diário de Lisboa (in Portuguese). No. 21452. 9 May 1984. p. 14. Retrieved 15 March 2017.
^ abc"Sessão de boas vindas" [Welcome party]. Diário de Lisboa (in Portuguese). No. 21511. 19 July 1984. p. 15. Retrieved 15 March 2017.
^"Fernando Martins: respeito por todos" [Fernando Martins: Respect of everyone]. Diário de Lisboa (in Portuguese). No. 21504. 11 July 1984. p. 14. Retrieved 15 March 2017.
^"Ivici deixou o Benfica sem assinar contrato" [Ivic left Benfica without signing the contract]. Diário de Lisboa (in Portuguese). No. 21522. 1 August 1984. p. 13. Retrieved 15 March 2017.
^"Benfica promove Eusébio" [Benfica promotes Eusébio]. Diário de Lisboa (in Portuguese). No. 21524. 3 August 1984. p. 13. Retrieved 15 March 2017.
^"Benfica, que treinador?" [Benfica, what manager?]. Diário de Lisboa (in Portuguese). No. 21528. 8 August 1984. p. 13. Retrieved 15 March 2017.
^"Benfica: para começar já vence a concorrência" [Benfica: for starters, it already beats its competition]. Diário de Lisboa (in Portuguese). No. 21520. 30 July 1984. p. 13. Retrieved 15 March 2017.
^"Benfica perde e decepciona" [Benfica disappoints]. Diário de Lisboa (in Portuguese). No. 21526. 6 August 1984. p. 16. Retrieved 15 March 2017.
^"Violência e mau génio com justa condenação" [Violence and bad temper with just sentence]. Diário de Lisboa (in Portuguese). No. 21531. 11 August 1984. p. 14. Retrieved 15 March 2017.
^"Sporting vence torneio internacional" [Sporting wins international tournament]. Diário de Lisboa (in Portuguese). No. 21532. 13 August 1984. p. 16. Retrieved 15 March 2017.
^ ab"Benfica empata em Setúbal e em Bragança" [Benfica draws in Setúbal and in Bragança]. Diário de Lisboa (in Portuguese). No. 21537. 20 August 1984. p. 13. Retrieved 15 March 2017.
^"Benfica derrotou o Belenenses" [Benfica defeated Belenenses]. Diário de Lisboa (in Portuguese). No. 21554. 8 September 1984. p. 16. Retrieved 15 March 2017.
^"Troféu de Honra para o Sporting" [Taça de Honra goes to Sporting]. Diário de Lisboa (in Portuguese). No. 21628. 7 December 1984. p. 15. Retrieved 15 March 2017.
^"Benfica partiu hoje e joga Domingo" [Benfica flew today and plays Sunday]. Diário de Lisboa (in Portuguese). No. 21523. 2 August 1984. p. 15. Retrieved 15 March 2017.
^"Trocas e baldatrocas" [Trading and more trading]. Diário de Lisboa (in Portuguese). No. 21442. 26 April 1984. p. 15. Retrieved 14 March 2017.
^"Filipovic confirma Boavista" [Filipovic confirms Boavista]. Diário de Lisboa (in Portuguese). No. 21480. 11 June 1984. p. 15. Retrieved 15 March 2017.
^"Varzim aposta na juventude" [Varzim bets on youth]. Diário de Lisboa (in Portuguese). No. 21522. 1 August 1984. p. 13. Retrieved 17 March 2017.