British light-heavyweight Joshua Buatsi made a winning yet unimpressive start to life under new promoters with a unanimous decision over Parker in the Manchester arena.
The Olympic medal winner's punch output appeared to earn him a split decision in a competitive ten-round bout at the Manchester venue.
But Parker landed significant shots, connecting with powerful single shots in a match where the techniques failed to mesh, with excessive holding marring the contest.
The scoring judges judged it 96-94 to the winner, with the final judge a 95-95 draw.
"It wasn't my finest display but what defines champions? They succeed," Buatsi said in the arena as he was met by disapproval from the spectators.
The British fighter bounced back after his first professional defeat - an epic battle with his previous opponent in February - to earn a twentieth professional win.
Several boxing experts believed the challenger, 31, deserved the win but the contender experienced the second loss of his 28-bout professional journey.
The Champion Claims Triumph in Uneventful Affair
The fighter's advancement has plateaued in recent years through promotional disputes and long spells of inactivity.
Earlier forecast as the future of the British fight scene, he now is positioned trying to achieve expectations - maybe in what appears to be a ultimate opportunity - under new promotional backing.
He started carefully, with neither fighter prepared to overcommit in a tentative early stages.
The challenger, whose only previous defeat came at super middleweight against John Ryder in two years ago after suffering a hand injury in the contest, was making just his second bout at light heavyweight.
By the halfway stage, the underdog had kept it close, making life awkward for the favorite, who utilized a tight guard to edge the cleaner periods.
The spectators' acceptance decreased because of frequent holding, with Parker slipping to the canvas various instances during clinches.
Parker closed well, but several stanzas were challenging to assess. Although, previous titleholder Carl Frampton - working with the broadcast network - had it significantly in favor for the challenger, giving Buatsi just only one stanza.
The victor moves on, but with the likes of heavy hitter David Benavidez, and Eastern European fighter Bivol dominating the weight class, the journey to titles - judging by this showing - still looks steep.
Ricky Hatton Homage Inspires All-Manchester Contest
In the secondary fight, Lyndon Arthur overcame Rea by close verdict in a outstanding Manchester vs Manchester fight to win the European light heavyweight championship.
The venue fell silent for a profoundly moving memorial ahead of the contest as a bell ceremony sounded in memory of local hero Hatton, who succumbed 46 years old in last month.
It was the premier televised fight night in the city since Hatton's passing. As the last bell ended, the quiet gave way to a chant of "there's just one Ricky Hatton".
The action within the ring equaled the sentiment. The eventual winner was floored by a left hook directly to the jaw in the early round, standing uncertainly to his position on the referee's count.
But the red-colored equipment of Arthur soon came forward again. On the opposite side, Rea - in rival City blue - was damaged soon, heavy swelling appearing under his face as the pair exchanged hard punches.
The challenger, 27, landed power punches but the champion, 34, matched the intensity with effective uppercuts as the intensity hardly diminished over the full distance.
Arthur edged the result with scoring tallies of even score, close margin and 115-112, but each competitor were persistent and full of heart, everything their inspiration the legend represented.
