Leigh Leopards 20 Wakefield Trinity 19: Cruel relegation for Super League mainstays on dramatic night
Trinity fought to the very last and beyond in a breathless contest that highlighted the undeniable spirit that has got the club out of so many scrapes in the past.
Two-try Lee Kershaw was in floods of tears at full-time after failing to pull off an intercept before O'Brien's winner, just one of several opportunities that went begging for Trinity with the game and their top-flight status on the line.
Once the dust settles, they can have few complaints but the manner of their relegation will sting.
For Castleford, it was a feeling of relief after confirming their safety despite suffering a heavy defeat at Wigan Warriors.
The Tigers found two wins at the right time to avoid the drop – including a vital victory at Belle Vue – but they remain in the firing line as rugby league enters a new era.
The introduction of a grading system leaves both clubs in limbo, Wakefield in particular after dropping out of Super League.
Chairman John Minards is optimistic that Trinity will make the grade but that will do little to appease frustrated supporters who have been helpless to prevent a slow death.
Wakefield have escaped relegation on the final day five times since joining Super League in 1999 and demonstrated their powers of recovery to stay up last season.
But their luck has finally run out after coming into this year with a squad ill-equipped for the rigours of a top-flight campaign.
When injuries ripped through Mark Applegarth's side, Trinity were only heading one way despite belated attempts to improve the squad.
That they took it to the penultimate round was an achievement in itself after losing their first 14 games.
A mid-season rally gave Wakefield the scent of another great escape but there was no way back after suffering a crushing defeat at the hands of relegation rivals Castleford.
Before a ball was kicked in 2023, the general view was that Leigh would join Trinity in the scrap for survival following their promotion from the Championship.
Instead, the Leopards are preparing for a first Super League play-off campaign and the prospect of a home eliminator after cementing fourth place with a hard-fought win in front of an expectant crowd.
Leigh threatened to make light work of their visitors when Tom Briscoe opened the scoring inside the opening four minutes.
A break by Oliver Gildart left Wakefield on the back foot and Briscoe touched down in the corner from O'Brien’s smart kick.
Before Trinity's heads could drop, they were gifted a try against the run of play.
Tom Amone was guilty of pushing a pass that was never on just inside his own half, the ball went to ground and Liam Hood scooped it up to race over under the posts.
Trinity defended their line with grit, one lapse aside that allowed Josh Charnley to cut back inside to finish all too easily.
Wakefield vented at the officials following a series of decisions that went against them but 12-6 was a fair reflection of the opening quarter.
Trinity were up against it when Kevin Proctor was sin-binned for a late hit in a five-minute stint to forget off the bench – and the visitors paid the price for the experienced forward's indiscretion just after the restart following an error by Jay Pitts.
There appeared to be nothing on when Jack Hughes got the ball on the last but he benefited from soft defence to get the ball down in heavy traffic.
Although Ben Reynolds sent his conversion attempt wide, there was a sense that Wakefield's race was run.
In a repeat of the first half, Leigh gifted Trinity a route back into the game.
Ben Nakubuwai threw a loose pass that went to ground and Kershaw pounced to scorch away for a 60-metre try.
Luck was with Wakefield but there was no fortune about the try that got them level.
Josh Griffin earned Trinity perfect field position with a charge down and Kershaw flew over in the corner at the end of a crisp move.
Mason Lino missed from the touchline but Wakefield had hope.
Reynolds and Lino traded penalties in a tense finale to match anything Super League has produced in recent times.
O'Brien appeared to have won it in normal time for Leigh with a nerveless drop goal but Trinity were never going to go quietly.
Luke Gale held his nerve in the final minute to knock over a one-pointer and send the match to golden point, setting up the most dramatic of finishes.
Gale, Lachlan Lam, O'Brien and Max Jowitt all missed drop-goal attempts as the tension reached fever pitch.
Knowing a draw would send them down, Trinity had a chance to win it with time running out when a Leigh pass found Kershaw.
But the winger could not take it in and the stage was set for O'Brien to land the final blow, just as he did to Hull KR in 2016.
Leigh Leopards: O'Brien, Briscoe, Gildart, Chamberlain, Charnley, Reynolds, Lam, Amone, Ipape, Mulhern, Hughes, O'Donnell, Davis. Substitutes: Mellor, Wardle, Nakubuwai, Holmes.
Wakefield Trinity: Jowitt, Kershaw, Croft, Franco, Lineham, Gale, Lino, Battye, Hood, Whitbread, Ashurst, Griffin, Pitts. Substitutes: Tanginoa, Kay, Proctor, Salabio.
Referee: Tom Grant.