José Bosingwa and Leandro will sit out FC Porto's opening SuperLiga fixture at the weekend and the following month.
The 22-year-old Bosingwa took a blow to his left knee on Monday and Porto were awaiting test results before announcing the midfield player's recovery time, which has been placed at one month. It is the second injury Bosingwa has suffered during pre-season, the first to his right knee at a training camp in the Netherlands.
Leandro, a 26-year-old Brazilian left-back, damaged his thigh in Tuesday's session and also faces a month out. Porto begin their bid to regain the Portuguese crown from SL Benfica against CF Estrela da Amadora at the Estádio do Dragão on Sunday, four days before they learn their three group stage opponents at the Champions League draw in Monaco.