Blanc, now manager of Bordeaux, has long since coveted his former Reds colleague to bolster his defence for next season's Champions League campaign.
He holds no further hope of snaring Silvestre, however, insisting his compatriot will remain in Manchester.
"Mikael Silvestre? It is finished," Blanc told a press conference, in reference to his quest to sign the United defender. "He has decided to stay in Manchester for his last season there."
Silvestre missed much of last season with a cruciate knee ligament injury, but returned in the latter stages to provide experienced defensive cover.
Sir Alex Ferguson is keen to keep his squad together, and Silvestre seems set to stay in Manchester for what would be a 10th season at Old Trafford.