Hristo Stoichkov has warned Pedro he must not join Manchester United because Louis van Gaal is a "mediocre" manager who will "destroy" him.
United want to sign Barcelona forward Pedro as a replacement for Angel di Maria, who joined Paris St Germain for £44.3million last week.
The 28-year-old is regarded as one of the best attackers in Spain, but has become frustrated at his lack of first-team football following the arrival of Luis Suarez and Neymar, who have formed a deadly three-man attack at the Nou Camp with Lionel Messi.
Former Barcelona striker Stoichkov thinks the Canary Islander would be making a huge mistake if he moved to Old Trafford, however, because he believes Van Gaal is a poor coach.
The Bulgarian clashed with Van Gaal during the Dutchman's first spell in charge of Barcelona and he clearly does not have a high opinion of the 64-year-old.
"I would never be under the orders of this Dutchman (Van Gaal)," Stoichkov told Spanish radio station Onda Cero.
"I would never leave if I was Pedro because if he goes there he would no longer be a footballer. I hope Pedro listens to me and he tells them (United) 'I am staying at Barcelona'."
Van Gaal sold Stoichkov to CSKA Sofia 17 years ago, but the pain of leaving the Spanish giants is clearly still raw for the Bulgarian.
"He makes players suffer," said Stoichkov, who branded Van Gaal "scum" during an interview in March.
"He is destroying all the players because he is so mediocre, players have left because of him.
"He destroys clubs, he did it with Barcelona, and after they take years to build.
"He has spent £200million (at United) and the other day I saw his first game of the season: disastrous. He won 1-0 (against Tottenham) because of an own goal."
Stoichkov thinks Barca have no reason to sell the Spain international even though he is not considered a first-team regular.
"Barcelona don't need money, whether it's 20, 30, or 50 million," he said.
"Pedro is a symbol of Barcelona, a type of player with energy, he fights to make himself great, why do Barcelona need to sell him?
"Why should they say goodbye to a player like this?"
Pedro looks set to start for Barcelona in their European Super Cup clash against Sevilla on Tuesday because Neymar has been ruled out through illness.
Speaking on the eve of the match in Georgia, Barcelona coach Luis Enrique claimed the saga was close to being concluded.
"Pedro's future will be resolved shortly because there is not long to go until the transfer market closes," the Barcelona coach told a press conference in Tbilisi.