Saint-Étienne took the lead in the 22nd minute of the contest decided at Stadio Olimpico.
The Nigerian midfielder finished well; rifling home a low half-volley into the bottom-left corner past the Saint-Étienne goalkeeper, Stephane Ruffier.
Onazi was a bundle of activity all night and was booked by Turkish referee, Halis Özkahya in the 25th minute.
