The 24-year-old has made a real name for himself this season in the heart of the Granata's promotion-winning defence, but his club will do their utmost to hold onto him
The 24-year-old centre-back, who can also play at left-back, played a key role in the Granata's promotion to Serie A this season and his fine form was rewarded with a place in Italy's squad for Euro 2012.
Ogbonna has been linked with a host of top clubs, including AC Milan, in recent weeks, but Petrachi has warned all interested parties that Torino have no intention of letting their youth-team product leave on the cheap.
"We have already spoken about this several times: only a sensational offer will shift our stance," he told Sky Sport Italia.
When asked if a bid of €12 million would be acceptable, Petrachi replied: "I believe that it would require much more [than that]."
Ogbonna, who earned his second Azzurri cap against the United States in February, is reportedly in contention to start against Spain in Gdansk on June 10.