Gerard Pique claims it is difficult for Barcelona to buy central defenders because such players rarely adapt well to the team's style of play.
Goal revealed in July that the Blaugrana had made a £25 million move for Chelsea stopper David Luiz, but Jose Mourinho has since denied that the Brazilian will be allowed to leave Stamford Bridge.
Pique believes the club's pursuit of defensive reinforcements is made more difficult by the distinctive way they set out on the pitch.
"It's hard to find the right profile [of player] because our style of play is unique," the 26-year-old told reporters in Thailand, where club begin their pre-season tour of Asia. "Experience says it's not easy to find a centre-back for Barca."
Pique went on to insist that team-mate Cesc Fabregas is eager to stay at the club despite continued interest in the midfielder from Manchester United.
"I've always looked very calmly at it. It's normal to receive offers when you're that good, but he has always told me he wants to stay and succeed at Barca."
The Spaniard also expressed his admiration for Barcelona talisman Lionel Messi, stating his belief that the Argentine continues to set the standard for the rest of the footballing world.
"Every year Messi seems to reach his limit, but he always ends up exceeding that. He is the best."