Barcelona have confirmed that defender Thomas Vermaelen has suffered a calf injury.
The 30-year-old has started just six games in La Liga this season, with his last appearance coming in the 6-0 win over Getafe on March 12.
Barca announced on Monday that the former Arsenal captain has picked up a muscle problem but would not place a timeframe on his possible recovery.
"The Belgian defender suffered an elongation in the soleus of his right leg," the club confirmed.
Vermaelen joins fellow defender Jeremy Mathieu and midfielder Rafinha on the sidelines as Barca prepare for their Champions League quarter-final second leg with Atletico Madrid on Wednesday.