British light-heavyweight Joshua Buatsi secured a victory yet disappointing beginning to his career under recent management with a decision win over Parker in the Manchester arena.
The Olympic medal winner's activity level appeared to earn him a judges' verdict in a tight 10-round fight at the Manchester venue.
But the challenger landed significant shots, landing some telling individual punches in a contest where the techniques failed to mesh, with excessive holding spoiling the fight.
The officials had it 96-94 to the winner, with the third a 95-95 draw.
"It wasn't my greatest performance but what defines champions? They prevail," the victor stated in the ring as he was greeted with boos from the crowd.
The Londoner returned to winning ways after his first professional defeat - an memorable fight with Callum Smith in last winter - to claim a 20th pro success.
Various analysts thought the challenger, 31, merited the win but the British boxer endured the second setback of his 28-bout professional journey.
The Champion Claims Triumph in Uneventful Encounter
Buatsi's progress has stalled in the past few years through promotional disputes and extended periods of lack of fights.
Previously predicted as the next star of UK boxing, he now is positioned trying to realize his potential - possibly in what feels like a final roll of the dice - under fresh management.
He opened tentatively, with neither fighter ready to take risks in a calculated initial rounds.
The challenger, whose single earlier setback came at super-middleweight against John Ryder in 2022 after suffering a hand injury during the bout, was making just his second fight at light-heavyweight.
By the middle rounds, the underdog had kept it close, creating difficulties for the favorite, who operated with a solid defense to narrowly win the better periods.
The audience's tolerance wore thin during constant clinching, with the challenger falling to the floor multiple occasions during clinches.
The underdog ended stronger, but multiple periods were challenging to assess. Although, former world champion the boxing analyst - providing analysis for Dazn - had it strongly leaning for Parker, giving Buatsi just a single round.
Buatsi advances, but with the presence of hard hitter David Benavidez, and Russian star Dmitry Bivol leading the category, the journey to titles - judging by this showing - still appears challenging.
Ricky Hatton Tribute Motivates All-Manchester Contest
In the secondary fight, Lyndon Arthur overcame Bradley Rea by split-decision in a excellent all-Manchester battle to secure the European light-heavyweight championship.
The venue became quiet for a deeply poignant memorial ahead of the contest as ten bells sounded in honor of local hero Ricky Hatton, who died 46 years old in recently.
It was the initial significant broadcast match card in the urban center since the passing of Hatton. As the last bell disappeared, the quiet gave way to a shout of "there's just one Hatton".
The competition during the bout reflected the feeling. The eventual winner was knocked down by a significant blow flush on the jaw in the early round, rising shakily to his feet on the count of eight.
But the traditional red shorts of Arthur soon came forward again. From the other corner, the opponent - in competitive blue - was marked up soon, noticeable damage forming under his eye as the fighters landed powerful shots.
Rea, 27, connected with strong blows but Arthur, thirty-four, responded in kind with powerful upward punches as the intensity hardly diminished over the full distance.
The victor narrowly won the decision with official scores of draw, close margin and clearer margin, but the two athletes were determined and courageous, all the qualities their idol the legend represented.
