The Spanish defender was forced off the pitch early on in the Champions League draw with Atletico Madrid on Tuesday night after landing awkwardly, and he is now expected to miss the second leg of the quarter-final against Diego Simeone's side.
"After only 10 minutes of play Gerard Pique suffered a bad fall," a club statement confirmed. "The player asked to be subbed off after he noticed pain in his hip due a pelvic contusion.
"The medical team advise he will be out for four weeks."
Marc Bartra replaced Pique in central defence against Atletico, and could be asked to deputise in the 27-year-old's absence.