UK light-heavyweight Joshua Buatsi secured a victory yet unimpressive debut to his career under new promoters with a unanimous decision over Parker in the Manchester arena.
The Olympic medal winner's work rate likely gained him a split decision in a close 10-round contest at the boxing arena.
But Parker had his moments, delivering effective individual punches in a contest where the styles didn't complement each other, with excessive holding spoiling the fight.
Two judges judged it 96-94 in favor to Buatsi, with the third a 95-95 draw.
"It wasn't my best showing but what defines champions? They prevail," the victor stated in the arena as he was greeted with negative reactions from the crowd.
The Londoner bounced back after his first professional defeat - an epic battle with his previous opponent in February - to secure a 20th pro success.
Some ringside observers felt the challenger, thirty-one, deserved the decision but the Derbyshire fighter experienced the second setback of his 28-fight professional journey.
Buatsi Earns Triumph in Uneventful Match
The fighter's advancement has stalled in recent times through contract problems and considerable time of inactivity.
Previously predicted as the rising talent of UK boxing, he now is positioned trying to realize his potential - perhaps in what seems like a ultimate opportunity - under recent support.
He opened tentatively, with both competitors ready to take risks in a tentative opening few rounds.
The challenger, whose single earlier setback came at super middleweight against John Ryder in two years ago after breaking his hand mid-fight, was competing in only his second bout at light-heavyweight.
By the middle rounds, the underdog had made it competitive, making life awkward for the favorite, who operated with a tight guard to narrowly win the cleaner rounds.
The spectators' acceptance diminished because of frequent holding, with the challenger falling to the floor several times during clinches.
The underdog finished the stronger, but several stanzas were challenging to assess. Nevertheless, previous titleholder the boxing analyst - working with Dazn - had it strongly leaning for the challenger, awarding Buatsi just one round.
The victor moves on, but with the presence of power puncher David Benavidez, and Eastern European fighter Bivol dominating the weight class, the road to world glory - based on this performance - still looks steep.
Hatton Homage Inspires All-Manchester Fight
In the co-main event, Lyndon Arthur overcame Bradley Rea by close verdict in a terrific Manchester vs Manchester battle to secure the European light-heavyweight belt.
The stadium grew hushed for a deeply poignant tribute ahead of the contest as a bell ceremony tolled in memory of local hero Ricky Hatton, who passed away at age 46 in September.
It was the premier televised boxing event in the city since Hatton's passing. As the concluding sound faded, the stillness became a roar of "there's only one Ricky Hatton".
The action inside the ropes reflected the feeling. The eventual winner was sent to the canvas by a significant blow flush on the face in the second round, standing uncertainly to his footing on the eight count.
But the traditional red equipment of Arthur soon came forward again. Across the ring, the opponent - in opposing blue - was damaged soon, heavy swelling forming under his face as the fighters landed hard punches.
Rea, 27, delivered effective strikes but Arthur, 34, responded in kind with stinging uppercuts as the pace hardly diminished over the full distance.
The victor barely secured the decision with official scores of 114-114, close margin and 115-112, but the two athletes were determined and brave, everything their hero Hatton represented.
