UK light heavyweight Joshua Buatsi made a winning yet unimpressive debut to life under new promoters with a unanimous decision over Parker in the Manchester arena.
The Olympic bronze medallist's punch output appeared to earn him a split decision in a close ten-round contest at the boxing arena.
But the challenger had his moments, connecting with powerful individual punches in a fight where the techniques failed to mesh, with constant grabbing disrupting the action.
The officials scored it 96-94 to the winner, with the final judge a 95-95.
"It wasn't my best display but how do champions respond? They prevail," Buatsi stated in the arena as he was greeted with boos from the audience.
The British fighter got back to winning after his maiden career setback - an memorable fight with his previous opponent in last winter - to earn a 20th pro success.
Some ringside observers believed Parker, 31, should have been awarded the victory but the British boxer endured the second defeat of his 28-match career.
Buatsi Earns Victory in Dull Affair
His career development has plateaued in the past few years through management issues and extended periods of inactivity.
Once tipped as the next star of British boxing, he now is positioned trying to realize his potential - possibly in what appears to be a last chance - under recent support.
He began cautiously, with neither fighter ready to take risks in a tentative early stages.
Parker, whose only previous defeat came at super-middleweight against John Ryder in two years ago after suffering a hand injury during the bout, was making just his second bout at light-heavyweight.
By the halfway stage, the underdog had made it competitive, making life awkward for Buatsi, who worked behind a solid defense to edge the better rounds.
The audience's tolerance decreased amid regular grabbing, with the challenger going down several times during grappling.
The underdog ended stronger, but several stanzas were difficult to score. However, former world champion the boxing analyst - providing analysis for Dazn - had it particularly wide for the challenger, giving Buatsi just a single round.
The victor progresses, but with the likes of power puncher Benavidez, and Eastern European fighter Dmitry Bivol leading the category, the journey to titles - on this evidence - still appears challenging.
Ricky Hatton Memorial Fuels Manchester Derby Fight
In the co-main event, Arthur defeated Bradley Rea by divided decision in a terrific local rivalry contest to win the European light heavyweight title.
The stadium became quiet for a extremely emotional memorial ahead of the contest as 10 bells sounded in honor of local hero Ricky Hatton, who succumbed aged 46 in recently.
It was the premier televised fight night in the location since Hatton's passing. As the last bell ended, the silence transitioned to a shout of "only one Hatton".
The action within the ring equaled the sentiment. Arthur was sent to the canvas by a significant blow directly to the face in the early round, rising shakily to his feet on the count of eight.
But the traditional red equipment of Arthur soon came forward again. On the opposite side, Rea - in competitive blue - was marked up quickly, noticeable damage appearing under his face as the duo exchanged punishing blows.
The challenger, 27, landed power punches but the champion, 34, responded in kind with stinging uppercuts as the intensity rarely dropped over the full distance.
Arthur edged the decision with scoring tallies of even score, 115-113 and 115-112, but the two athletes were relentless and brave, everything their inspiration the legend stood for.
