Ghanaian forward Abdul Majeed Waris will replace injured striker Soares in Porto's home fixture against Sporting Lisbon on Friday night.
The Ghana International came on for Soares in Porto's 5-1 thrashing of Portimonense last weekend.
FC Porto already prepare the classic of Friday against Sporting with another name in the clinical report.
Soares, who scored one of the goalscoring goals in a 5-1 win at Portimão, was replaced by Majeed Waris in the 71st minute, having suffered a left thigh injury, the club said on the official website.
"As planned, Soares underwent a medical examination that confirmed a lesion in the left thigh, contracted in the game with the Algarve," a stetement on the club's website read.