Barcelona says captain Carles Puyol fractured his right cheekbone in the 2-1 league victory at Osasuna.
Barcelona says further medical scans will be done on Monday to determine the extent of the injury and how long it will sideline the 34-year-old defender.
Barcelona's next game is in midweek at Real Madrid for the second leg of the Spanish Supercopa, which the Catalan side leads 3-2.
The injury happened in the closing moments at the Reyno de Navarra Stadium after a brush with Osasuna's Roland Lamah.
Puyol finished the match as Barcelona won a third straight game to start the season.
Puyol has endured a number of injuries in the last few seasons, including surgery to his right knee that kept him from helping Spain win EURO 2012.