Nabuli has chosen to switch codes to rugby union and will play for the Queensland Reds next year.
While O’Brien has been rumoured to join the Eels in 2016 to bolster their front row stocks.
Read the complete Dragons release below.
Both players made their respective first-grade debuts for the Club in the opening round of this season against the Melbourne Storm, with Nabuli making a total of 11 appearances and O’Brien three to date.
“Both Eto and Rory have received opportunities elsewhere commencing next season,” said Head Coach Paul McGregor.
“Everyone at the Dragons wishes them both all the very best for their respective futures and thank them for their services to our Club.”