At a time when the champions sit in fourth position in the standings, the home side are 13th despite putting together a run of three games without defeat.
Match preview
On the back of winning last season's title, Benfica supporters would have had high hopes for 2023-24, yet their side have work to do to achieve their priority objectives for the season.
To their credit, Roger Schmidt's side have recorded maximum points in their last four domestic fixtures, scoring 11 goals in the process, but two of those victories have been by one-goal margins.
Lowly Vizela pushed their more illustrious opponents all the way last weekend, halving the deficit with 20 minutes remaining before failing to earn a share of the spoils as Benfica held on for a 2-1 win.
However, the Eagles were brought back down to earth in midweek as they succumbed to a 2-0 defeat at home to Red Bull Salzburg in the Champions League.
The early dismissal of Antonio Silva proved costly as the Austrian giants posted an impressive win at Estadio aa Luz, leaving Benfica in a position where they will be desperate to bounce back on Sunday.
Portimonense should provide another test for Benfica, though, having put together a three-game undefeated streak for the first time since April.
After registering draws versus Arouca and Estrela, Paulo Sergio's side travelled to high-flying Vitoria de Guimaraes and came away with a 2-1 triumph.
Alvinegros had trailed for much of the contest before Carlinhos netted twice - the first goal coming from the spot - in the final nine minutes to pull off the surprise win.
With trips to Porto and Braga to come in the four-game run following Sunday's encounter, Sergio knows that Portimonense cannot necessarily play with complete freedom when hosting the champions, despite their minnow status.
Portimonense Primeira Liga form:
Portimonense form (all competitions):
L
L
L
D
D
W
Benfica Primeira Liga form:
Benfica form (all competitions):
L
W
W
W
W
L
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Team News
Having been withdrawn before the half-hour mark last time out, midfielder Lucas Ventura may miss out for Portimonense.
If Ventura is not passed fit, right-sided player Igor Formiga is on standby to deputise, although that would likely lead to a reshuffle.
Goncalo Costa may be preferred to Moustapha Adjalian Seck at left-back after making an impression as a substitute against Vitoria.
Joao Mario will be refreshed to start for Benfica having been withdrawn on the back of Silva's sending off against Salzburg.
With players being rested during the final 20 minutes, it is plausible that Schmidt will select much of the same starting lineup.
However, Arthur Cabral could be handed a chance down the centre of the attack if Petar Musa does not shake off an injury issue.
Portimonense possible starting lineup:
Silvestre; Pedrao, Alemao, Relvas, Costa; Carlinhos, Dener, Ventura; Jasper, Paulinho, Varela
Benfica possible starting lineup:
Trubin; Bah, Silva, Otamendi, Aursnes; Neves, Kokcu; Di Maria, Rafa, Joao Mario; Cabral
We say: Portimonense 1-4 Benfica
Having stunned Vitoria last time out, Portimonense will back themselves to take something from a Benfica side that have not always been convincing this season. However, we feel that the 2022-23 title winners will be motivated to let out some frustration after their disappointment in the Champions League.