Blackburn suffered a blow to their English Premier League survival hopes on Wednesday when Paraguayan striker Roque Santa Cruz underwent knee surgery.
The 27-year-old has been out of action since the 0-0 draw with Everton at the beginning of March.
"He's had a little arthroscopy to clean out floating fragment in the knee," said Blackburn Rovers manager Sam Allardyce. "I'm not putting a time limit on his return but hopefully it wont be long."
Santa Cruz was the subject of repeated enquiries from Manchester City during the January transfer window, and has made just seven appearances for Blackburn since 1 February, scoring twice.
Blackburn are currently four points off the relegation zone in the English Premier League.