On 29 June 2017, club president
Luís Filipe Vieira gave the motto for the coming season, "
Rumo ao Penta", and promised a renewed ambition to conquer an unprecedented fifth-straight Primeira Liga title for Benfica. The following day, manager
Rui Vitória explained his approach to the new season: "We know that there's a goal previously assumed by the President and the best way to achieve it is to go on together, like it was the first time. It is fundamental to have the first time ambition. Humble and focused so that it can happen." Despite the ambition, on 31 July, Vieira said "one can mortgage a title or another but not the future [of the club]", referring to a strategy of managing the club's debt through the sale of players.
Transfers Haris Seferovic,
Filip Krovinović,
Martin Chrien and
Bruno Varela transferred to Benfica.
Diogo Gonçalves and
Rúben Dias were promoted from
Benfica B and
João Carvalho integrated the team after a loan spell at
Vitória de Setúbal. Benfica lost three players from the starting 11 before the season started: on 1 June,
Ederson signed with
Manchester City for €40 million; on 14 June,
Victor Lindelöf left to
Manchester United for €35 million; and on 14 July,
Nélson Semedo moved to
Barcelona for €30.5 million. On 31 July, referring to the club's sales, Vieira said, "Until we do not have control over the debt, we will not stop selling." Benfica finished third in the Swiss tournament after a 5–1 defeat to
Young Boys. The team redeemed itself with a victory in the
Algarve Football Cup thanks to a brace by newly signed Seferovic. On 26 July, Benfica played a behind-closed-doors friendly against
Swindon Town at Futebol Campus, where Seferovic and
Andrija Živković scored for Benfica in a 2–1 win. Once again, Benfica stood powerless in the Emirates Cup. By losing both matches, the team repeated its
fourth-place finish achieved in 2014. Due to
Chapecoense's cancellation, Benfica did not host the
Eusébio Cup in the pre-season for the first time since its first edition in 2008. As with the previous season, Benfica kept struggling with player injuries. On 17 June,
Álex Grimaldo did not take part in Spain's squad for the
UEFA European Under-21 Championship due to a "little injury" resulting in him missing the start of Benfica's pre-season. Nine days after signing with Benfica, Krovinović underwent surgery on 23 June to correct a left inguinal hernia. He was one of three players absent from the squad who travelled to Switzerland, along with
Luisão (right knee injury) and
Eduardo Salvio (right tibiotarsal sprain).
André Almeida suffered a contusion on his right thigh, which prevented him from travelling to Algarve.
Supertaça Cândido de Oliveira For the opening match of the regular season, Benfica had five players on the injury list:
Júlio César, Živković, Carrillo, Horta and Mitroglou.
Andreas Samaris was also not an option because he was serving the first of a four-match suspension for having punched
Diego Ivo on 9 April. Benfica defeated
Vitória de Guimarães 3–1 with goals from
Jonas, Seferovic and
Raúl Jiménez.
Raphinha scored for Vitória. It was the first time Benfica managed to win back-to-back
Super Cup trophies. Seferovic made his official debut for Benfica and Varela, a former Benfica B player, debuted for the first team after being called up to the substitutes' bench nine times since 2011. Grimaldo suffered a muscular injury on his right leg and was substituted for
Eliseu in the 75th minute.
Primeira Liga With three consecutive victories, Benfica achieved their best start in the Primeira Liga since the
2004–05 season. By scoring a goal in each of those matches, Seferovic managed to score in his first four official appearances for Benfica, repeating the feat of
Mário Coluna and
Nolito (all behind
Eusébio). A 1–1 draw at
Rio Ave, in a match where
Jardel was substituted due to injury on his right tight, left Benfica in third place of the
league by the end of August. After losing 2–1 at
Boavista and drawing 1–1 with
Marítimo at the
Estádio dos Barreiros, Benfica were 5 points behind leaders
Porto before October's international break. Benfica won their next three matches but maintained the point difference to the top of the table. By scoring, at least, one goal per match between Match 3 and Match 11, Jonas became the third Benfica player to score in nine consecutive Primeira Liga matches after
Julinho (1949–50) and Eusébio (1964–65). He improved his mark by scoring in the following match. Benfica ended 2017 with 36 points, 3 less than their
two rivals. 2018 started with the
Lisbon derby at home, which ended in a 1–1 draw. Midway through January, in a match against
Chaves, Krovinović suffered a season-ending injury to his right knee. The results of round 21 lifted Benfica into second place, thus surpassing
Sporting CP on the account of the goal difference criteria. Despite the ascendant in the league table, Benfica still could not avoid player injuries; Salvio suffered another right knee injury and was submitted to an
arthroscopy. After a 5–0 home win on 3 March, Benfica achieved five consecutive victories for the first time during the season. On 10 March, Benfica assured a place in Europa League's qualifying rounds. On round 28, Benfica regained the first place, with a one-point lead over Porto. The nine-match win streak came to an end after a 1–0 home defeat in
O Clássico, a result that also culminated in a return to the second place. It was the fourth match in a row Benfica could not beat Porto at the Estádio da Luz (two draws and two defeats), a negative record achieved for the third time. With a 3–2 home loss to
Tondela, Benfica suffered two consecutive league defeats at Estádio da Luz for the first time since the
2008–09 season. With a 1–0 home win against
Moreirense on the last matchday, Benfica attained 80+ points in the Primeira Liga for the fourth consecutive season. Due to the defeat of Sporting CP at
Funchal, Benfica's result allowed the club to secure the second place and the qualification for the
2018–19 UEFA Champions League third qualifying round.
UEFA Champions League Twenty five players made Benfica's list for the group stage of the
UEFA Champions League. Benfica started the European campaign with a 2–1 home defeat to
CSKA Moscow, in what was their first loss of the season. On 27 September, Benfica moved to the bottom of Group A after a 5–0 away loss to
Basel. It was Benfica's biggest defeat in the UEFA Champions League (tied with the loss to
Borussia Dortmund in the
1963–64 European Cup) and
second overall in international competition. On 18 October, Svilar became the youngest goalkeeper to play in Champions League, in a match where Benfica suffered a 1–0 home loss against
Manchester United. Benfica was eliminated from European competitions after a 2–0 away loss to CSKA Moscow. By failing to score, Benfica put an end to
Igor Akinfeev's streak of 43 straight UEFA Champions League group stage matches without a clean sheet. Also, with this result, Benfica lost 6 consecutive European matches for the first time in their history. This entry increased to seven consecutive losses with a 2–0 home defeat on the last matchday. Benfica became the nineteenth club, and the first seeded into Pot 1, to
finish the UEFA Champions League group stage with 0 points.
Taça da Liga Benfica started with a 1–1 home draw against Braga, in a match where Krovinović made his official debut. It was the first time since 2007 that Benfica did not win in the competition at the
Estádio da Luz, ending a 20-home-game win run. After the final whistle, Samaris was involved in an altercation with
Paulinho and saw a yellow card. Six days later, Samaris was punished by the Disciplinary Committee with a three-match suspension, missing Primeira Liga fixtures. Benfica continued to perform under expectations and, on 20 December, they had another home draw, despite having a 2–0 lead before the break. Two days later, they were eliminated from the competition after Vitória de Setúbal defeated Braga. With a third draw in the last match, Benfica ended their participation in the
Taça da Liga without a single win for the first time.
Taça de Portugal On 14 October, Benfica beat
Olhanense 1–0 away from home in the third round of
Taça de Portugal. The match was initially scheduled to be played at the
Estádio José Arcanjo but was changed to the
Estádio Algarve. Four players (Júlio César, Eliseu, Jardel and Jonas) missed the game due to injury, while Douglas, Carvalho and Svilar made their debut for Benfica. On 13 December, for the second time in this season, Benfica could not win at the
Estádio dos Arcos. After a 2–2 draw at the end of regulation time,
Hélder Guedes scored the winning goal for Rio Ave, thus eliminating the reigning title holders. Luisão got injured (right thigh muscle injury) during the second half's stoppage time, leaving Benfica to play the extra time in numerical disadvantage.
Aftermath On 11 June, Vieira regretted the club's disappointing season overall and took responsibility for not managing to win the
penta and for the negative campaign in the Champions League. Despite that, he denied disinvestment in the football team and highlighted its competitiveness. Former Benfica player and sporting director
António Simões criticised the team's lack of quality and said, "With this squad and other rivals reinforcing themselves, Benfica will not win again." By failing to win the Primeira Liga and the Taça de Portugal, Benfica did not qualify for the
2018 edition of the Supertaça Cândido de Oliveira, breaking a streak of four consecutive appearances at the competition. Five Benfica players were called by their respective national team to take part in the
2018 FIFA World Cup: Dias (
Portugal), Salvio (
Argentina), Živković (
Serbia), Seferovic (
Switzerland) and Jiménez (
Mexico). On 7 July, Benfica announced that
Shéu Han, the team's technical secretary since 1989, decided to leave his post. On 31 July,
Paulo Lopes announced his retirement via
Instagram, making this his last season as a professional footballer. Similarly, Eliseu also retired after his contract was not renewed, even though he said in a 2019 interview that his career was on standby. Although Luisão integrated the squad for the
following season, his last professional match was on round 34 of Primeira Liga, before retiring on 25 September. ==Club==