UK light heavyweight Joshua Buatsi made a winning yet disappointing debut to life under fresh promotional backing with a decision win over Parker in the Manchester arena.
The Olympic medal winner's punch output seemingly secured him a judges' verdict in a tight 10-round fight at the Manchester venue.
But Parker landed significant shots, landing some telling clean blows in a match where the techniques didn't complement each other, with excessive holding disrupting the contest.
The officials scored it 96-94 for to Buatsi, with the third a even score.
"It wasn't my best display but how do champions respond? They prevail," Buatsi commented in the ring as he was greeted with boos from the audience.
The British fighter got back to winning after his initial pro loss - an epic battle with his previous opponent in last winter - to secure a twentieth professional win.
Several boxing experts thought the challenger, thirty-one, deserved the victory but the contender endured the second setback of his 28-match career.
The Champion Claims Win in Slow Match
His career development has plateaued in recent times through contract problems and extended periods of inactivity.
Earlier forecast as the rising talent of UK boxing, he now stands trying to fulfil that early promise - maybe in what seems like a last chance - under new promotional backing.
He started carefully, with neither fighter willing to take risks in a cagey opening few rounds.
The challenger, whose single earlier setback came at super-middleweight against John Ryder in 2022 after damaging his hand in the contest, was making just his second fight at the higher weight class.
By the fight's midpoint, Parker had made it competitive, making life awkward for the favorite, who operated with a tight guard to narrowly win the cleaner rounds.
The spectators' acceptance wore thin during constant clinching, with the challenger slipping to the canvas several times during close exchanges.
Parker finished the stronger, but several stanzas were hard to judge. Although, former world champion Carl Frampton - working with Dazn - had it significantly in favor for the challenger, scoring for Buatsi just only one stanza.
Buatsi moves on, but with the presence of heavy hitter Benavidez, and Eastern European fighter Bivol dominating the weight class, the path to championship success - judging by this showing - still looks steep.
Ricky Hatton Homage Inspires Local Rivalry Fight
In the secondary fight, Lyndon Arthur overcame Bradley Rea by divided decision in a excellent Manchester vs Manchester fight to capture the continental title.
The stadium grew hushed for a profoundly moving homage prior to the bout as 10 bells tolled in remembrance of local hero Hatton, who succumbed aged 46 in last month.
It was the first major televised match card in the location since the passing of Hatton. As the last bell faded, the quiet transitioned to a shout of "there's just one Hatton".
The action during the bout equaled the emotion. Arthur was knocked down by a left hook flush on the face in the initial stage, getting up unsteadily to his position on the eight count.
But the traditional red shorts of Arthur soon advanced again. Across the ring, the opponent - in rival City blue - was injured quickly, noticeable damage developing under his eye as the duo landed punishing blows.
Rea, twenty-seven, delivered effective strikes but Arthur, 34, responded in kind with effective uppercuts as the intensity rarely dropped over 12 rounds.
Arthur narrowly won the verdict with official scores of 114-114, close margin and clearer margin, but both fighters were determined and courageous, everything their inspiration Hatton stood for.
