Success at Famalicao last week could provide momentum for the 11th-placed home side, while Petit's visitors lost at home to ruthless leaders Sporting Lisbon.
Prior to their invaluable win at Estadio Municipal de Famalicao, Gil Vicente had succumbed to defeat in four of their last six outings - their most recent home loss coming against title-chasing Benfica just before Christmas.
Now, a run of seven points recorded from their past four games has given head coach Ricardo Soares more reason for optimism, as his side have moved a little further away from the Primeira Liga basement.
A first-half Claude Goncalves half-volleyed strike from the edge of the area proved enough for the Galos to triumph last week - the France-born midfielder registering his first goal of the season.
Despite a squad packed with Brazilian imports, this season Gil Vicente have rarely provided the drama and creativity of the legendary poet after whom they were named.
Lisbon's often overlooked 'third club', Belenenses are familiar with battling against the drop and are currently stuck among the morass of teams just above the dotted line.
In 14th place following an expected 2-1 defeat by Sporting, they will nonetheless have taken some solace from their showing in the capital derby.
Having had 10 shots on goal to the leaders' five - and with visiting goalkeeper Antonio Adan being named 'Man of the Match' - they came close to causing a shock. In fact, goalscorer Miguel Cardoso, on loan from Dynamo Moscow, had a penalty saved by former Real Betis stopper Adan with the scores tied at 1-1.
Even at the age of 26, Cardoso's career has been a peripatetic one so far. In his second season at Tondela, he racked up eight Primeira Liga goals and six assists, leading to an unlikely move to Russia.
After a loan move to FC Tambov failed to work out, in the summer the former Deportivo La Coruna man returned to his home country on a temporary deal. Despite his penalty miss, Cardoso will have gleaned confidence from his goal last time out and can provide a serious threat to Gil Vicente's defence on Monday.
Belenenses head to Barcelos with ex-Portugal international Petit's win percentage since taking charge a year ago sitting at an unimpressive 29% and his team have scored only six goals so far this season. If they are to avoid demotion to Liga 2, then those statistics must improve soon.
Gil Vicente Primeira Liga form: LLWDLW
Gil Vicente form (all competitions): DWDLWW
Belenenses Primeira Liga form: DDDWLL
Belenenses form (all competitions): WDWLWL
Visiting manager Petit generously cancelled a training session scheduled for New Year's Day ahead of Monday night's game. However, the Belenenses boss has defensive selection problems to solve.
First-team regulars Cafu Phete and Tomas Ribeiro are currently suspended, while Henrique is injured, so Danny Henriques could be joined by Samir Banjai, Luca van der Gaag and Goncalo Silva at the back. Alternatively, Tiago Esgaio could feature in a three-man defence.
Winger Lourency has impressed in recent games for Gil Vicente and has again been linked with a move away from the club this month, but will start in a front three - with either Renan or Lino leading the line.
Ricardo Soares prefers a 4-3-3 setup and has spoken of the difficulty of facing a Belenenses outfit which defends deep, so Japan Under-20 international Kanya Fujimoto could feature from the bench in order to unlock the visitors' defence late on.
Gil Vicente possible starting lineup:
Denis; Pereira, Nogueira, Rodrigao, Talocha; Mineiro, Goncalves, Carvalho; Lourency, Lino, Leautey
Belenenses possible starting lineup:
Oliveira; Henriques, Esgaio, Silva; Calila, Sithole, Taira, Lima; Varela, Cardoso, Sousa
We say: Gil Vicente 1-1 Belenenses
As Belenenses rarely give much away - and have beaten Braga and troubled Sporting in recent weeks - Gil Vicente will have their work cut out to claim maximum points at home.
A low-scoring draw appears the most likely outcome, as both sides look set for a drawn-out battle for Liga NOS salvation on the cards.