The hosts entered the weekend top of the league, while Chaves remain pointless after a dreadful start.
Match preview
Very few Portuguese football fans would have envisaged Boavista making such an incredible start.
Petit's men lost both of their pre-season friendlies comfortably without scoring, and then went out of the Taca da Liga at the first hurdle, losing to lower-league Leiria.
Being given an opening day task of trying to overcome champions Benfica looked daunting given the lack of confidence they may have brought into the season.
However, Boavista stunned last season's champions, with Robert Bozenik's last-gasp goal sealing a 3-2 win for the underdogs.
Since then, Boavista have gone on to record away successes at both Portimonense and Estoril to keep pace with those at the top.
Petit has oversaw an unbeaten start with 10 points and topped the table before the start of the weekend's action.
Porto playing, and winning, on Friday night though means Boavista have relinquished top spot for now, but a win will see them return top, should Sporting not thrash Moreirense on Sunday.
The hosts will fancy their chances of doing so given the woeful start their guests have made to the season.
Sitting rock bottom, Chaves are the only side still without a point in the Primeira Liga so far.
A goal difference of -10 means that even an unlikely win here will not lift Jose Gomes's men out of the relegation zone.
Their two away results so far offer very little to be encouraged about - losing 2-0 at Rio Ave and taking a 5-0 thrashing at the hands of Farense.
In the 10 games between now and Christmas, Chaves will only face Benfica out of the traditional top four, so there will then be a clearer picture regarding their fate this season once they face many of the sides around them.
These two sides met on the final day last season, and Chaves had three men sent off as Boavista cruised to an easy victory.
However, in their four trips to this province of Porto this century, Chaves are yet to taste defeat, winning once and recording three draws, with their last defeat coming in 1998.
Boavista Primeira Liga form:
Boavista form (all competitions):
Chaves Primeira Liga form:
Chaves form (all competitions):
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Team News
Boavista will be without Vincent Sasso and goalkeeper Cesar, who is recovering from an ACL injury here.
Bruno Onyemaechi was the only Boavista man away on international duty, representing Nigeria, and he should start in defence.
Only Sporting Lisbon's Paulinho has scored more goals than Bozenik this season, with the recent Feyenoord recruit currently on three goals in four games.
Chaves will be without Ruben Lameiras, as a knee injury will see him miss at least a month's action.
The new signing only made his full debut against Moreirense last time out, but he was taken off injured at half-time.
Another new face Leandro Sanca could be the man to come in for Lameiras, joining Thibang Phete in the side after the South African made his debut shortly before the international break.
Boavista possible starting lineup:
Joao Goncalves; Pedro Malheiro, Awaziem, Abascal, Onyemaechi; Perez, Makouta, Reisinho; Tiago Morais, Bozenik, Salvador Agra
Chaves possible starting lineup:
Hugo Souza; Joao Correia, Bruno Rodrigues, Ygor Nogueira, Langa; Bernardo Sousa, Nwakali, Phete, Abass, Sanca; Hernandez
We say: Boavista 2-0 Chaves
Boavista's strong start looks set to continue, playing a woefully out-of-form Chaves side on home soil here.