UK light-heavyweight Joshua Buatsi secured a victory yet disappointing beginning to his career under new promoters with a decision win over Parker in the Manchester arena.
The Olympic bronze medallist's punch output likely gained him a majority decision in a tight 10-round bout at the boxing arena.
But Parker had his moments, landing some telling clean blows in a fight where the approaches didn't complement each other, with constant grabbing spoiling the action.
Two judges scored it 96-94 for to the winner, with the remaining official a 95-95 draw.
"It wasn't my finest showing but how do champions respond? They succeed," Buatsi stated in the ringside as he was met by negative reactions from the spectators.
The British fighter bounced back after his initial pro loss - an epic battle with his previous opponent in last winter - to secure a twentieth professional win.
Some ringside observers thought the challenger, thirty-one, deserved the victory but the Derbyshire fighter suffered the second loss of his 28-match professional journey.
Buatsi Claims Triumph in Slow Match
Buatsi's progress has plateaued in recent times through contract problems and considerable time of lack of fights.
Earlier forecast as the rising talent of the British fight scene, he now is positioned trying to realize his potential - maybe in what seems like a ultimate opportunity - under new promotional backing.
He started carefully, with both competitors prepared to take risks in a tentative early stages.
Parker, whose sole prior loss came at the lower weight class against John Ryder in two years ago after damaging his hand during the bout, was competing in only his second fight at light-heavyweight.
By the halfway stage, the underdog had stayed in contention, making life awkward for Buatsi, who worked behind a solid defense to narrowly win the more effective periods.
The crowd's patience decreased because of constant clinching, with the challenger slipping to the canvas multiple occasions during close exchanges.
Parker closed well, but many rounds were challenging to assess. Nevertheless, former world champion the boxing analyst - commentating on Dazn - had it strongly leaning for Parker, giving Buatsi just a single round.
Buatsi progresses, but with the likes of heavy hitter David Benavidez, and Russian star Dmitry Bivol ruling the division, the path to championship success - judging by this showing - still appears challenging.
Ricky Hatton Memorial Inspires Local Rivalry Contest
In the co-main event, Lyndon Arthur overcame Bradley Rea by divided decision in a terrific local rivalry contest to win the European light heavyweight title.
The stadium fell silent for a deeply poignant memorial prior to the bout as a bell ceremony tolled in memory of the city's native Ricky Hatton, who succumbed at age 46 in last month.
It was the premier televised boxing event in the location since the passing of Hatton. As the concluding sound faded, the silence became a chant of "there's only one Ricky Hatton".
The fighting within the ring reflected the feeling. The eventual winner was knocked down by a left hook flush on the chin in the early round, getting up unsteadily to his feet on the eight count.
But the traditional red attire of Arthur soon came forward again. On the opposite side, the opponent - in competitive blue - was damaged early, heavy swelling developing under his orbital area as the fighters traded powerful shots.
The challenger, twenty-seven, delivered effective strikes but Arthur, thirty-four, fought fire with fire with stinging uppercuts as the intensity seldom decreased over twelve rounds.
Arthur narrowly won the result with judges scorecards of even score, 115-113 and wider gap, but both fighters were persistent and full of heart, everything their idol Hatton embodied.
