Chelsea have agreed to promote Costa to Atletico Madrid for £57m after he went AWOL this summer time.
Conte textual content Costa to inform him he may in finding a new membership initially of the summer time and Balague believes that gave Chelsea little leverage when negotiating his sale.
Costa scored 20 objectives to lend a hand Chelsea win the name ultimate season however has been changed via Alvaro Morata, who already has six in six.
But Balague thinks Conte can have were given more cash for Costa had he now not proven his hand so early.
He instructed Sky Sports: “It used to be a huge mistake on Antonio Conte’s phase to ship a textual content to Costa announcing he used to be now not sought after, as a result of he weakened the location of Chelsea.
“Chelsea sought after 70m euros, Atletico says, they were given 55m plus 10m. It continues to be a giant charge, one Atletico hasn’t ever paid.
“But he do not have despatched it. I am lovely positive if you are a director at Chelsea you would want he hadn’t too.
“It gave the desires of Costa a giant push, as a result of he may all the time say: ‘glance, they are not looking for me’.
“That’s why he felt he did not wish to return to coach or play with the reserves, or anything else like that. It performed totally into his arms.
“But Chelsea kind of were given what they sought after for him, as soon as Conte made up our minds he did not need to stay.”
Costa refused to go back to London after calls to coach with the reserves in Cobham.
He claimed to had been handled like a felony via the membership, a advice that used to be laughed off via Conte in a strange press convention previous this season.