British light heavyweight Joshua Buatsi earned a win yet disappointing beginning to life under new promoters with a decision win over Parker in the Manchester arena.
The Olympic medal winner's work rate seemingly secured him a majority decision in a competitive ten-round bout at the Manchester venue.
But the challenger found success, delivering effective clean blows in a contest where the styles didn't complement each other, with excessive holding marring the fight.
The officials judged it 96-94 to Buatsi, with the remaining official a even score.
"It wasn't my greatest showing but what do champions do? They win," the victor commented in the ringside as he was greeted with negative reactions from the spectators.
The Londoner bounced back after his first professional defeat - an epic battle with Callum Smith in last winter - to claim a twentieth professional win.
Some ringside observers felt Parker, 31, merited the victory but the contender endured the second setback of his 28-bout career.
Buatsi Earns Victory in Slow Encounter
Buatsi's progress has stalled in recent times through contract problems and considerable time of inactivity.
Previously predicted as the rising talent of UK boxing, he now is positioned trying to achieve expectations - possibly in what feels like a ultimate opportunity - under recent support.
He started carefully, with neither fighter ready to take risks in a tentative opening few rounds.
Parker, whose single earlier setback came at super middleweight against his former opponent in two years ago after damaging his hand during the bout, was participating in his second bout at the higher weight class.
By the middle rounds, the underdog had kept it close, creating difficulties for the favorite, who utilized a tight guard to edge the cleaner rounds.
The audience's tolerance wore thin amid frequent holding, with the challenger falling to the floor multiple occasions during grappling.
Parker closed well, but many rounds were difficult to score. Nevertheless, previous titleholder the boxing analyst - commentating on the broadcast network - had it particularly wide for Parker, awarding Buatsi just one round.
Buatsi moves on, but with the caliber of heavy hitter David Benavidez, and Russian star Dmitry Bivol dominating the weight class, the road to world glory - based on this performance - still looks steep.
Hatton Tribute Inspires All-Manchester Battle
In the co-main event, Lyndon Arthur defeated Rea by divided decision in a outstanding all-Manchester battle to capture the continental championship.
The arena became quiet for a profoundly moving memorial prior to the bout as ten bells rang in memory of Manchester's own Ricky Hatton, who succumbed 46 years old in recently.
It was the premier televised boxing event in the city since Hatton's passing. As the concluding sound faded, the silence gave way to a roar of "there's just one Hatton".
The competition inside the ropes matched the feeling. Arthur was sent to the canvas by a left hook directly to the face in the initial stage, standing uncertainly to his footing on the count of eight.
But the red-colored equipment of the fighter soon advanced again. Across the ring, the opponent - in competitive blue - was damaged soon, significant bruising developing under his face as the duo exchanged punishing blows.
Rea, twenty-seven, landed power punches but Arthur, 34, fought fire with fire with stinging uppercuts as the intensity hardly diminished over 12 rounds.
Arthur narrowly won the result with official scores of even score, 115-113 and wider gap, but each competitor were determined and full of heart, exactly what their idol Hatton represented.
