Parramatta Eels centre Tom Opacic has been officially ruled out of the NRL grand final against the Penrith Panthers on Sunday evening.

Opacic missed last week's preliminary final against the North Queensland Cowboys with a hamstring injury that he has originally suffered against the Canberra Raiders during a blowout semi-final win the week before.

The centre was confident he would be able to return for the decider, but ultimately has fallen short, with Eels' medical staff ruling him out on Thursday.

Opacic was only named in the Eels' extended squad for the game on Tuesday afternoon, with Bailey Simsonsson - who was his last minute replacement for the trip to Townsville - named instead.

That means he likely retains his place for the decider, with Brad Arthur confirming the news to the media after training on Thursday.

"Tom won't play, we wanted to give him every opportunity (to play)," Arthur said at the grand final press conference on Thursday.

"We're devastated for Tom.

"I remember the day before his debut he guaranteed the group he be would ultra reliable and he has been that for us. It is sad for Tom, but he is still part of the 22."

It means Opacic has played his last game for the Eels, with the centre set to head to England in 2023 after not securing a new deal to remain in the blue and gold.

Opacic finishes his time in the NRL with 82 games, 18 of which have come this season, and a total of 39 for the Eels since he joined the club at the start of 2021.

The NRL grand final kicks off at 7:30pm (AEST) on Sunday evening at Homebush, where a sell out crowd will be on hand.