British light-heavyweight Joshua Buatsi secured a victory yet unimpressive debut to his career under fresh promotional backing with a points victory over Parker in the Manchester arena.
The Olympic medal winner's work rate likely gained him a split decision in a tight 10-round bout at the boxing arena.
But Parker had his moments, delivering effective individual punches in a contest where the techniques never quite clicked, with frequent clinching disrupting the fight.
The scoring judges judged it 96-94 in favor to Buatsi, with the third a 95-95.
"It wasn't my greatest showing but what defines champions? They prevail," Buatsi stated in the ring as he was faced boos from the spectators.
The British fighter bounced back after his first professional defeat - an thrilling contest with Callum Smith in last winter - to claim a twentieth professional win.
Various analysts believed Parker, thirty-one, deserved the win but the British boxer suffered the second setback of his 28-bout career.
Buatsi Secures Triumph in Dull Affair
Buatsi's progress has stalled in the past few years through management issues and considerable time of inactivity.
Once tipped as the rising talent of UK boxing, he now finds himself trying to realize his potential - maybe in what seems like a final roll of the dice - under recent support.
He started carefully, with both competitors prepared to be aggressive in a calculated opening few rounds.
Parker, whose sole prior loss came at the lower weight class against John Ryder in 2022 after breaking his hand mid-fight, was participating in his second bout at the higher weight class.
By the halfway stage, the underdog had kept it close, creating difficulties for Buatsi, who utilized a solid defense to narrowly win the better periods.
The audience's tolerance diminished amid constant clinching, with Parker going down several times during grappling.
Parker finished the stronger, but many rounds were difficult to score. However, ex-champion the boxing analyst - working with the broadcast network - had it strongly leaning for the challenger, giving Buatsi just only one stanza.
The victor moves on, but with the presence of heavy hitter Benavidez, and Russian star Bivol ruling the division, the journey to titles - based on this performance - still looks steep.
Hatton Tribute Motivates Local Rivalry Battle
In the secondary fight, Lyndon Arthur beat Bradley Rea by split-decision in a outstanding all-Manchester contest to capture the European light heavyweight title.
The stadium fell silent for a extremely emotional homage before the fight as 10 bells sounded in memory of the city's native Hatton, who died aged 46 in recently.
It was the initial significant broadcast boxing event in the urban center since Hatton's passing. As the concluding sound ended, the silence transitioned to a shout of "there's only one Ricky Hatton".
The competition inside the ropes reflected the sentiment. The eventual winner was sent to the canvas by a left hook squarely on the face in the initial stage, getting up unsteadily to his position on the referee's count.
But the traditional red equipment of the fighter soon came forward again. On the opposite side, Rea - in rival City blue - was injured quickly, noticeable damage forming under his eye as the pair traded punishing blows.
Rea, twenty-seven, landed power punches but the champion, thirty-four, fought fire with fire with stinging uppercuts as the pace hardly diminished over the full distance.
Arthur narrowly won the decision with judges scorecards of even score, 115-113 and 115-112, but each competitor were determined and full of heart, everything their hero the legend represented.
