Real Madrid defender David Alaba had to be substituted with a hamstring strain during his side's 3-1 win over Osasuna in La Liga on Wednesday night.
The Austria international picked up the problem in the latter stages of the first half at Estadio El Sadar and did not appear for the second period, with Dani Carvajal entering as his replacement.
Alaba's injury has placed the defender as a major doubt for next week's Champions League semi-final first leg with Manchester City at the Etihad Stadium.
However, Los Blancos boss Carlo Ancelotti has said that the club are "optimistic" over the situation, claiming that his withdrawal was "a precaution".
"We are optimistic with Alaba. He had a strain, we took him off as a precaution," Ancelotti told reporters after the clash with Osasuna.
Alaba arrived at Real Madrid on a free transfer from Bayern Munich last summer and has been a vital player for the club this season, making 44 appearances in all competitions, contributing three goals and four assists in the process.
Los Blancos are now in a commanding position at the top of the La Liga table, sitting 17 points clear of second-placed Atletico Madrid, although third-placed Barcelona, who are 18 points behind, have two games in hand.
