Players who leave Barcelona of their own accord when they are young should not be re-signed by the club later in their careers, former captain Xavi Hernandez has told Diario Sport.
Barca have been strongly linked this summer with Arsenal right-back Hector Bellerin, who left the club as a 16-year-old to try his luck in England.
However, Xavi, who currently plays for Qatari club Al Sadd, says that if it were up to him Barca should not even consider making a move for the Spain international.
"I haven't seen him play a lot, but what I will say is I find it difficult to accept signing a player who was already at the club," Xavi said when asked if he would sign Bellerin.
Gerard Pique has proved a major success since returning from a spell at Manchester United in 2008, while Xavi had pressed for the return of Cesc Fabregas from Arsenal in 2011, saying the midfielder had "Barca DNA."
He added: "Of course it can work out, but I would not sign players who leave. Why are they leaving at 16, 17? I find it baffling. I just don't understand it."
Asked if he was referring to the departures of Jordi Mboula and Eric Garcia this summer to Monaco and Manchester City respectively, he said: "Yes, their decisions surprised me. I wouldn't buy them back in the future. That would be my philosophy. You were at the club, you decided to leave, so you don't then come back.
"I understand that if you want to leave there must be a reason, like [Jon] Toral, who has an English mother. Fine. But that's how it is [if you leave], the train has passed.
"A player can't leave during the development process. When I was 16 I didn't want to leave. I felt that I was in the best place I could possibly be. If Chelsea or [Manchester] United came in for me, I would have said no."
There are exceptions to the rule, Xavi added, pointing out that Gerard Deulofeu was sold by the club, which was not his choice, while Aleix Vidal and Jordi Alba were released in their teenage years.
To solve the problem of players leaving, Xavi, who has said he wants to return to the club as coach in the future, wants a renewed focus on making sure academy prospects are brought through to the first team.
"Barcelona need to nurture their own homegrown players," he said. "They can't leave like this. Playing in the first team has never been easy. I had a tough time getting there and getting settled in the time.
"Right now there are players like [Carles] Alena, Marlon [Santos] and [Marc] Cucurella who are showing potential. But it's difficult to be a top player at 19."