Porto manager Sergio Conceicao is uncertain about the severity of Vincent Aboubakar's injury after the forward limped off in a Portuguese Primeira Liga match.
Aboubakar was in action for only 38 minutes as the Dragons defeated Pacos de Ferreira 2-0 on Monday.
The 27-year-old was replaced by Cape Verde Islands forward Ze Luis who later sealed maximum points for the hosts after Senegal's Mamadou Ndiaye opened the scoring at Estadio do Dragao.
The victory moved Porto to two points behind league leaders Benfica but Conceicao ruled Aboubakar's injury as the only negative highlight of the encounter as they await his medical examination.
"That is the only negative point of today's game. We know it was a muscle problem, but we don't know the severity of the injury," the manager told the club website.
Aboubakar recently returned from a lengthy spell on the sidelines after undergoing surgery for a ruptured anterior cruciate ligament in his knee last September.