Nacional, meanwhile, have lost only one of their opening eight games in all competitions and could move as high as fifth place with a victory away from home.
Portimonense look destined for another relegation battle, with their poor start to the campaign seeing them lose five of their opening seven league games.
The Portimao-based side also lost their Taca de Portugal tie last weekend against third division outfit UD Leiria, who narrowly beat them by a 1-0 scoreline.
Paulo Sergio has an uphill task to get his side climbing the table away from danger but will feel that this weekend's match is a good opportunity to start picking up points.
Portimonense will take confidence from their last meeting with Nacional when they convincingly beat them 5-1 in the 2018-19 campaign.
Securing their second league victory on Sunday could see the home side climb three places up to 15th in the table, two points clear of the relegation zone.
Nacional – who were crowned champions of the second tier last season – have alternated between relegation and promotion in each of the last four campaigns but will be hoping that their solid start in the Primeira Liga will give them a good platform to survive.
Luis Freire's side have lost only one of their opening seven top-flight matches, which was a 2-1 defeat away to Braga in October. They have also drawn four games and won the other two, including the 2-1 victory over Gil Vicente in their last league match.
Nacional head into Sunday's fixture after an entertaining tie in the Taca de Portugal, which saw them come from behind to win 3-2 in extra time against Casa Pia on Wednesday.
A victory against Portimonense would be the third in a row for the Funchal-based outfit and would also see them go five matches unbeaten in all competitions.
Portimonense Primeira Liga form: LLWLLL
Portimonense form (all competitions): LWLLLL
Nacional Primeira Liga form: WDLDDW
Nacional form (all competitions): DLDDWW
Portimonense midfielder Lucas Fernandes, who has played a major role for the club this season, has been ruled out for the rest of the campaign with an anterior cruciate ligament injury. Brazilian compatriot Luquinha is likely to come into the side as his replacement.
Nacional right-back Kalindi remains out with a knee injury, while left-back Witi is also unavailable as he has tested positive for coronavirus. Joao Vigario is set to come into the starting lineup as his replacement.
Striker Brayan Riascos, who scored a brace in the 3-2 win over Casa Pia, is likely to start once again up front.
Portimonense possible starting lineup:
Samuel; Moufi, Antonio, Willyan, Cande; Dener, Luquinhas, Sa; Oliveira, Fabricio, Morte
Nacional possible starting lineup:
Guimaraes; Freitas, Henrique, Kal, Vigario; Azouni, Micael, Koziello; Gorre, Riascos, Camacho
We say: Portimonense 0-2 Nacional
Portimonense are unbeaten in their last three encounters with Nacional and are desperate to pick up points, however the visitors have looked stronger in recent weeks and should have enough quality to defeat the hosts and move into the top five of the Primeira Liga table.