British light heavyweight Joshua Buatsi secured a victory yet unimpressive debut to life under new promoters with a points victory 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 bout at the Co-op Live Arena.
But the challenger landed significant shots, landing some telling individual punches in a fight where the techniques didn't complement each other, with excessive holding disrupting the contest.
Two judges had it 96-94 for to Buatsi, with the remaining official a 95-95.
"It wasn't my finest performance but what do champions do? They prevail," Buatsi stated in the ring as he was met by boos from the audience.
The Londoner returned to winning ways after his initial pro loss - an epic battle with his previous opponent in February - to secure a twentieth professional win.
Some ringside observers thought Parker, 31, deserved the win but the contender experienced the second defeat of his 28-fight professional journey.
Buatsi Earns Win in Dull Affair
His career development has slowed in recent times through management issues and long spells of inactivity.
Previously predicted as the future of the British fight scene, he now is positioned trying to fulfil that early promise - maybe in what seems like a last chance - under recent support.
He opened tentatively, with both competitors ready to take risks in a tentative initial rounds.
Parker, whose single earlier setback came at the lower weight class against his former opponent in two years ago after damaging his hand mid-fight, was competing in only his second appearance at light heavyweight.
By the fight's midpoint, Parker had made it competitive, creating difficulties for Buatsi, who utilized a protective stance to edge the cleaner periods.
The spectators' acceptance decreased during constant clinching, with the challenger slipping to the canvas various instances during close exchanges.
Parker closed well, but many rounds were difficult to score. Nevertheless, ex-champion the boxing analyst - providing analysis for Dazn - had it strongly leaning for the challenger, scoring for Buatsi just one round.
Buatsi progresses, but with the caliber of heavy hitter David Benavidez, and Russian champion Bivol dominating the weight class, the path to championship success - on this evidence - still seems difficult.
Ricky Hatton Homage Fuels Manchester Derby Contest
In the supporting bout, Arthur defeated Rea by split-decision in a outstanding local rivalry battle to capture the European light heavyweight championship.
The arena fell silent for a extremely emotional homage ahead of the contest as 10 bells sounded in honor of Manchester's own Hatton, who succumbed 46 years old in last month.
It was the premier televised fight night in the city since the passing of Hatton. As the last bell faded, the quiet gave way to a chant of "only one Ricky Hatton".
The fighting within the ring reflected the emotion. Arthur was floored by a powerful punch flush on the chin in the second round, rising shakily to his footing on the referee's count.
But the traditional red equipment of the fighter soon came forward again. From the other corner, the opponent - in opposing blue - was marked up soon, significant bruising appearing under his eye as the fighters exchanged powerful shots.
Rea, 27, landed power punches but Arthur, thirty-four, matched the intensity with powerful upward punches as the action seldom decreased over 12 rounds.
Arthur narrowly won the result with scoring tallies of draw, close margin and clearer margin, but the two athletes were relentless and courageous, all the qualities their idol the legend represented.
