Boavista's first and second-choice goalkeepers both suffered serious knee injuries in the same training session leaving the Portuguese side with 17-year-old Tomé Sousa as their only fit keeper.
Boavista said João Gonçalves and Luís Pires ruptured their anterior cruciate ligaments during training, with both goalkeepers set for a long spell on the sidelines.
Gonçalves is the club's first-choice keeper after the 23-year-old played all 34 games last season and started the first four games of the new campaign.
"The two goalkeepers will undergo surgery in the next few days and a long recovery period is expected for both players," the club said on Thursday.
Sousa came through the club's academy and played for their youth side. He also has two caps with the Portugal under-18 team but he has never featured for the senior team at club or international level.
Boavista are 13th in the Primeira Liga standings after four games and Sousa could make his debut on Monday when they play away at Estrela da Amadora before they host Portuguese giants Benfica the following week.