He must, therefore, have been born with or had acquired equestrian status as Gallienus began the policy of excluding senators from high commands.
Against this Placidianus is credited by Alaric Watson[7] with suppressing a potentially dangerous revolt by Domitianus in the region south of Lake Geneva in 271.
However, the most likely location for Domitianus's suppression was the Gallic capital, Augusta Treverorum (Trier), where Placidianus was unlikely to have been operating in 271 so perhaps even this success must be denied him.
Whatever the reason for Placidianus's failure to come to the rescue of Autun, he obviously made a sufficiently good impression for Claudius's successor, Aurelian, to appoint him his Praetorian Prefect at or soon after his accession.
It is not known if he directly succeeded Aurelius Heraclianus, who had been Gallienus's last Praetorian Prefect and had probably colluded with Claudius and Aurelian in that Emperor's murder in 268.