British light heavyweight Joshua Buatsi secured a victory yet unimpressive debut to his career under recent management with a unanimous decision over Parker in the Manchester arena.
The Olympic medal winner's work rate appeared to earn him a majority decision in a tight ten-round fight at the boxing arena.
But Parker had his moments, delivering effective clean blows in a contest where the approaches never quite clicked, with constant grabbing spoiling the contest.
Two judges scored it 96-94 in favor to the winner, with the final judge a 95-95 draw.
"It wasn't my finest display but what defines champions? They succeed," the victor stated in the ring as he was greeted with negative reactions from the spectators.
The British fighter returned to winning ways after his maiden career setback - an epic battle with Callum Smith in February - to claim a 20th career victory.
Various analysts thought the challenger, thirty-one, deserved the victory but the contender endured the second setback of his 28-match professional journey.
The Champion Earns Triumph in Dull Encounter
Buatsi's progress has plateaued in the past few years through contract problems and long spells of inactivity.
Previously predicted as the future of UK boxing, he now finds himself trying to fulfil that early promise - maybe in what seems like a final roll of the dice - under recent support.
He began cautiously, with both competitors ready to overcommit in a cagey early stages.
The challenger, whose single earlier setback came at the lower weight class against John Ryder in two years ago after suffering a hand injury in the contest, was making just his second appearance at light heavyweight.
By the middle rounds, the underdog had made it competitive, causing problems for the favorite, who worked behind a solid defense to barely take the better periods.
The audience's tolerance diminished because of regular grabbing, with Parker falling to the floor several times during grappling.
The underdog ended stronger, but multiple periods were hard to judge. However, ex-champion Carl Frampton - providing analysis for Dazn - had it particularly wide for Parker, awarding Buatsi just one round.
The victor advances, but with the presence of power puncher David Benavidez, and Russian champion Bivol dominating the weight class, the path to championship success - judging by this showing - still looks steep.
Hatton Memorial Fuels All-Manchester Fight
In the secondary fight, Lyndon Arthur defeated Rea by divided decision in a outstanding local rivalry fight to capture the continental title.
The arena became quiet for a extremely emotional memorial ahead of the contest as a bell ceremony rang in remembrance of Manchester's own Ricky Hatton, who died at age 46 in recently.
It was the first major televised boxing event in the city since Hatton's passing. As the final chime disappeared, the silence gave way to a chant of "there's only one Ricky Hatton".
The fighting during the bout equaled the feeling. Arthur was sent to the canvas by a powerful punch squarely on the face in the early round, getting up unsteadily to his position on the referee's count.
But the Manchester United-red shorts of Arthur soon pressed ahead again. From the other corner, the opponent - in competitive blue - was marked up soon, significant bruising forming under his face as the pair landed powerful shots.
The challenger, twenty-seven, delivered effective strikes but Arthur, thirty-four, fought fire with fire with effective uppercuts as the action seldom decreased over 12 rounds.
Arthur edged the result with official scores of draw, close margin and 115-112, but both fighters were determined and full of heart, all the qualities their hero the legend stood for.
