Fabregas was jeered by some fans during the 2-1 victory over Athletic Bilbao on Sunday, but Pique believes that the whole team should be blamed for their recent disappointments.
"It isn't good to have fans whistling you - particularly at home," the Spaniard told reporters.
"I think it is a mistake to focus on just one player. Blame it on the players, okay, but not just Cesc.
"The season has not been good and I think we are all part of a group that haven't quite got things right."
Barcelona are currently second in La Liga, four points behind leaders Atletico Madrid.