Atletico Madrid have confirmed Raul Garcia suffered a sprained ligament in his right ankle during their 2-1 win over Porto on Tuesday.
The midfielder was forced off during the UEFA Champions League clash 11 minutes from time, in a game that saw Atletico come from a goal down to win.
After an MRI scan was performed, the club stated on their official Twitter account that the 27-year-old suffered a "grade-two sprain of the lateral ligament of the right ankle".
The injury was the only sour point of a night for Diego Simeone's men as they moved top of Group G thanks to an Arda Turan winner with just four minutes off normal time remaining.
Simeone urged his side to take each game at a time, but stated his delight at Atletico's performance at the Estadio do Dragao.
"We are very happy – we did a great job. It was a fantastic response to what was an adverse situation," he said.
"The first 25 minutes were hard for us, Porto were very strong then. When we changed our way of playing in midfield from the 30th minute, the game also changed.
"We made key tactical switches which helped us as we looked to play into spaces and get closer to their penalty area.
"The lead-up to our second goal was something we had worked on. There is happiness at achieving a very important result.
"It's incredible the reaction we produced tonight. Everyone put in a great performance. The team must be congratulated.
"We will go on taking things game by game."