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.
The Blaugrana have long been linked with a move for a number of centre-backs this summer - most notably Paris Saint-Germain star Thiago Silva - but Pique believes the club's pursuit of reinforcements at the back is made more difficult by the 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 a press conference in Thailand. "Experience says it's not easy to find a centre-back for Barca."
Pique went on to insists that team-mate Cesc Fabgregas is eager to stay at the club, despite continued interest 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 Lionel Messi, stating his belief that the Argentine continues to set the standard for the footballing world.
"Every year Messi seems to reach his limit, but he always ends up exceeding that. He is the best."