Maritimo lifted themselves off the foot of the table with a crucial 1-0 win over Farense last time out, while Saturday's hosts sit just two places and three points ahead in 14th spot.
Belenenses secured an impressive point last time out, as they held fourth-placed Braga to a 1-1 draw away from home.
However, that positive result followed a disappointing defeat for Petit's side, as they fell to a 2-0 loss at the hands of fellow strugglers Boavista, with Angel Gomes and Alberth Elis getting on the scoresheet.
As a result, O Belem have fallen down the Primeira Liga table, now sitting just three points ahead of Saturday's opponents in the relegation playoff place and five points above the automatic drop zone.
That means the hosts will be looking to return to winning ways on Saturday to put some more much-needed distance between themselves and the bottom three.
However, they take on a Maritimo side who are also in desperate need of a positive result to boost their chances of avoiding the drop.
Julio Velazquez picked up the most important result of his short spell as Maritimo manager last time out, as his side defeated fellow strugglers Farense 1-0 thanks to an Ali Alipour goal on the stroke of half time.
Velazquez took charge of the club following the recent departure of Milton Mendes, with the side sat bottom, and he has hugely boosted their chances of survival with two wins from his first four games to lift Os Verde-Rubros out of the automatic relegation zone.
Maritimo now sit in the relegation playoff place, just one point behind Boavista and three points behind Famalicao and Saturday's opponents.
That means Velazquez's men could move out of the bottom three with what would be a crucial victory on Saturday, offering a huge incentive to the side from Madeira as they go into this crucial encounter.
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Belenenses will be without midfielder Sphephelo Sithole, who will serve a suspension after he was shown his fifth yellow card of the season in the draw with Braga.
Thibang Phete will also remain out for this game, having missed the last two matches through injury.
However, Afonso Taira will return from his suspension to fill the gap left in midfield.
Pepa's decision to bring in Mateo Cassierra paid off with a goal in the draw with Braga, and he is expected to lead the line again, supported by the threat of Miguel Cardoso who has been moved to the left-hand side.
Maritimo could remain without their talisman Rodrigo Pinho, who missed the last game with an injury after serving a suspension.
Pinho tops Os Verde-Rubros' spring charts with nine goals in 16 league appearances, but Ali Alipour filled that void with a crucial goal last time out.
They will also be missing crucial midfielder Franck-Yves Bambock, who picked up his fifth yellow card of the season in the victory over Farense.
Belenenses possible starting lineup:
Kritsyuk; Silva, Henrique, Ribeiro; Esgaio, Taira, Sousa, Lima; Varela, Cardoso, Sousa
Maritimo possible starting lineup:
Abedzadeh; Santos, Junior, Andrade; Winck, Costa, Pelagio, Jean, Hermes; Tagueu, Alipour
We say: Belenenses 1-1 Maritimo
With a solid defensive outfit hosting a revitalised side under a new manager, this game could definitely go either way.
On this occasion, we predict a draw as both sides will be extremely fearful of a defeat which could see them fall further towards the threat of relegation