Porto's Cameroon striker Vincent Aboubakar faces a long spell on the sidelines after undergoing an ACL surgery.
The 26-year-old ruptured the anterior cruciate ligament in his left knee during the Portuguese champions' 1-0 win over Tondela on Friday.
Porto confirmed the surgery, which he had on Saturday, had gone successfully.
He will now miss his country's 2019 Nations Cup qualifying group fixtures in October and November.
Aboubakar also faces a race against time to be fit for next year's Africa Cup of Nations.
"Vincent Aboubakar was operated on by Professor José Carlos Noronha's team, following a complete rupture of the anterior cruciate ligament and internal lateral ligament of the left knee," Porto said on their website.
"The surgery was successful and the forward will be discharged in the coming days to start his rehabilitation process.”
Aboubakar was the hero as Cameroon came from behind to beat Egypt 2-1 and seal a fifth Africa Cup of Nations title in February 2017.