"I expected that the justifications for his detention are done with. It's no longer a secret," Al-Zayat said.
While Nasr was initially charged with membership of an illegal organisation, the charges were later dropped.
He was briefly released in April 2004 before being detained without charge under Egypt's emergency laws.
His lawyer had said he believed Nasr was re-arrested after ignoring warnings not to speak to anyone about the kidnapping and rendition.
Asked whether Nasr would remain silent as to what had happened to him during his time in detention, Al-Zayat said Nasr had "(chosen) to live, and avoid the painful years he's lived through ... he wants to raise his children."
Al-Zayat previously said state security prosecutors had denied him access to all of the case documents, including forensic reports which could have proven Nasr was tortured in detention.
Nasr had also attempted suicide on three occasions, Al-Zayat said.
The cleric's release comes as an Italian judge considers whether to charge 32 suspects, including Italy's former spy chief and a group of Americans believed to be CIA agents, in connection with the kidnap.
If tried, the case would be the first criminal procedure over renditions, one of the most controversial aspects of the Bush administration's "war on terror".
Washington acknowledges secret transfers of terrorism suspects to third countries, but denies torturing suspects or handing them to countries that do.