That's according to veteran forward Tyson Frizell, who says the Knights have the chance to end a "tough old year" with a fitting tribute to their departing coach.
Sunday's clash with Parramatta is both the last game of the regular season and of O'Brien's six-year coaching tenure, which began when the Knights were floundering.
It also now looms as crucial for Newcastle, with Gold Coast's win over Wests Tigers meaning a loss on Sunday will hand the Knights their first wooden spoon since 2017.
O'Brien arrived at a Newcastle side that had not played finals for six years and had claimed three spoons of their own in that dismal period.
He leaves having taken the Knights to the top eight in four of six seasons; only premiership-winning coach Michael Hagan has led Newcastle to as many finals series.
Dom Young, Leo Thompson and Fletcher Sharpe are among players who blossomed into star first-graders under O'Brien's management, which also brought Dane Gagai back to the club and signed NSW representative Frizell.
"He's done everything," Frizell said.
"The place was a little bit of a shambles before he came, and he's definitely left it in a better place. He's another guy that we'll be playing for."
Attacking impotence meant the Knights struggled for form early in the season, with injuries to Kalyn Ponga and Sharpe making things tricky as the year wore on.
But Frizell said his team would head to CommBank Stadium with fire in the belly.
"It's been a tough old year, so to go down there and put in a performance and hopefully get the result off the back of it is all our motivation," Frizell said.
"(This year) has been tough, some days are a lot tougher than others, but we're professional athletes.
"We get paid to do this every day. Even though it is tough, you get the job done, you come in, you train as hard as possible."
As the O'Brien era draws to a close, the Knights will come face to face with the future as they confront Eels playmaker Dylan Brown.
Brown will line up in the halves for Parramatta one last time before joining the Knights on the richest deal in NRL history next year.
"He's not worried about coming to Newcastle just yet. He'll be doing everything he can to play well for Parramatta, and the same for us," Frizell said.
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