Barcelona captain Carles Puyol is to have further tests to determine the extent of the fractured right cheekbone he suffered in the 2-1 win at Osasuna.
The 34-year-old defender sustained the injury in a late collision with Osasuna forward Roland Lamah.
A club statement read: "Medical tests confirmed that Carles Puyol has fractured his right cheekbone.
"The player will undergo further tests on Monday to determine the extent of the injury. Puyol broke his cheekbone when he collided with Lamah in one of the last plays of the match."
Lionel Messi scored twice in the last 15 minutes as Barca survived a scare against the 10-man hosts to continue their winning start to the new season.
Osasuna beat Barcelona 3-2 in last season's corresponding fixture and the Catalan giants looked in danger of being on the wrong end of another upset when Joseba Llorente volleyed the home side in front in the 17th minute.
But Messi equalised in the 75th minute, with Osasuna midfielder Patxi Punal subsequently sent off for taking his protests too far after Alexis Sanchez appeared to be offside when he received the ball earlier in the move.
The visitors quickly made the most of their man advantage as, in the 80th minute, summer signing Jordi Alba picked out Messi near the edge of the area and the Argentinian rolled a low shot into the far corner for the match-winner.
Barca coach Tito Vilanova was pleased with the way his team battled back after going a goal down.
"We place a lot of value on our capacity to fight back," he said. "This means we're strong because you have to be mentally strong and have ambition to win in this stadium.
"We created enough chances to win the match. It's twice as difficult to win here when you're behind because they'll try to break the rhythm of the game."