Real Madrid defender Marcelo suffered a suspected shoulder dislocation after the 2-1 win at Granada on 7 February. The Brazilian full back landed awkwardly after contesting an aerial ball with Isaac Success late in the match and had to depart Los Carmenes with his arm in a sling.
"We are not exactly sure about Marcelo. It is his shoulder, but we don't know," Real coach Zinedine Zidane told the club's official website.
Club director Emilio Butragueno said he was not aware of the severity of Marcelo's injury but that he hoped that it was only a minor knock, according to Spanish daily AS.
Luka Modric's sublime goal in the 85th-minute won the game for Real after Youssef El-Arabi had cancelled out Karim Benzema's opener.
Zidane heaped praise on Modric after the victory, which kept his team four points behind La Liga leaders Barcelona, and urged him to shoot more.
"He scored a fantastic goal that gave us a boost and, above all, the three points," he said. "I'm very happy with him because he needs to shoot more. He knows how to play in a lot of positions, also as a [number] 10."
Madrid struggled for fluency at Los Carmenes, but Zidane said it was to be expected away from home and declared himself satisfied with a result that keeps his team in the title race.
"I will focus on the win and the three points, which were very important for us," the Frenchman stated.
"When we play away we face a team and their fans. It is normal for it to be harder than at home. It was tough to get the win because it is a difficult pitch. The opponents have good players and make things difficult. That is football and we are not going to win every game easily."
Real's next assignment is a league fixture against Athletic Bilbao at the Santiago Bernabeu on 13 February before a Champions League trip to Roma on 17 February.