British light heavyweight Joshua Buatsi earned a win yet disappointing beginning to his career under fresh promotional backing with a unanimous decision over Parker in the Manchester arena.
The Olympic medal winner's work rate seemingly secured him a split decision in a competitive 10-round contest at the Manchester venue.
But the challenger found success, delivering effective clean blows in a match where the styles didn't complement each other, with frequent clinching disrupting the action.
The scoring judges judged it 96-94 for to the winner, with the remaining official a 95-95.
"It wasn't my best display but what defines champions? They prevail," Buatsi commented in the ringside as he was faced negative reactions from the spectators.
The British fighter got back to winning after his maiden career setback - an memorable fight with Callum Smith in February - to earn a 20th career victory.
Some ringside observers thought the challenger, thirty-one, deserved the victory but the British boxer endured the second loss of his 28-bout career.
The fighter's advancement has slowed in recent years through management issues and extended periods of inactivity.
Previously predicted as the rising talent of the British fight scene, he now is positioned trying to realize his potential - maybe in what appears to be a final roll of the dice - under fresh management.
He started carefully, with neither fighter willing to be aggressive in a tentative opening few rounds.
Parker, whose sole prior loss came at the lower weight class against his former opponent in 2022 after breaking his hand mid-fight, was competing in only his second fight at light heavyweight.
By the middle rounds, the underdog had kept it close, making life awkward for Buatsi, who worked behind a solid defense to edge the better stanzas.
The spectators' acceptance diminished amid frequent holding, with Parker going down multiple occasions during clinches.
Parker finished the stronger, but multiple periods were challenging to assess. Nevertheless, ex-champion Carl Frampton - providing analysis for the broadcast network - had it particularly wide for the challenger, awarding Buatsi just only one stanza.
Buatsi advances, but with the likes of hard hitter David Benavidez, and Russian star Bivol leading the category, the road to world glory - judging by this showing - still looks steep.
In the supporting bout, Arthur defeated Bradley Rea by close verdict in a outstanding local rivalry fight to capture the European light heavyweight belt.
The stadium fell silent for a profoundly moving homage before the fight as 10 bells sounded in memory of Manchester's own Hatton, who passed away aged 46 in recently.
It was the first major televised fight night in the urban center since Hatton's passing. As the concluding sound ended, the silence transitioned to a roar of "only one Ricky Hatton".
The fighting inside the ropes matched the emotion. Arthur was knocked down by a left hook directly to the jaw in the second round, standing uncertainly to his footing on the referee's count.
But the traditional red equipment of Arthur soon advanced again. Across the ring, Rea - in competitive blue - was damaged soon, noticeable damage appearing under his face as the pair traded powerful shots.
Rea, twenty-seven, landed power punches but Arthur, 34, matched the intensity with effective uppercuts as the action seldom decreased over twelve rounds.
The victor barely secured the decision with judges scorecards of draw, narrow lead and wider gap, but the two athletes were relentless and courageous, all the qualities their inspiration Hatton represented.
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