UK light heavyweight Joshua Buatsi secured a victory yet disappointing beginning to life under fresh promotional backing with a decision win over Parker in the Manchester arena.
The Olympic medal winner's activity level seemingly secured him a majority decision in a competitive 10-round bout at the boxing arena.
But Parker found success, landing some telling individual punches in a contest where the styles failed to mesh, with constant grabbing marring the contest.
The scoring judges scored it 96-94 in favor to Buatsi, with the remaining official a 95-95 draw.
"It wasn't my best display but how do champions respond? They win," the victor stated in the ringside as he was met by disapproval from the crowd.
The British fighter got back to winning after his maiden career setback - an epic battle with his previous opponent in February - to claim a twentieth professional win.
Various analysts believed Parker, thirty-one, deserved the win but the contender suffered the second loss of his 28-bout professional journey.
Buatsi Secures Victory in Uneventful Match
His career development has stalled in recent times through contract problems and long spells of inactivity.
Earlier forecast as the next star of the British fight scene, he now is positioned trying to fulfil that early promise - possibly in what seems like a ultimate opportunity - under fresh management.
He began cautiously, with both competitors willing to be aggressive in a cagey early stages.
The challenger, whose sole prior loss came at super-middleweight against his former opponent in two years ago after damaging his hand during the bout, was making just his second bout at the higher weight class.
By the fight's midpoint, the underdog had made it competitive, making life awkward for Buatsi, who worked behind a solid defense to narrowly win the better periods.
The crowd's patience diminished amid constant clinching, with the challenger slipping to the canvas multiple occasions during clinches.
The underdog finished the stronger, but multiple periods were difficult to score. However, ex-champion the boxing analyst - working with the broadcast network - had it strongly leaning for Parker, awarding Buatsi just a single round.
Buatsi progresses, but with the presence of power puncher David Benavidez, and Russian star Dmitry Bivol dominating the weight class, the path to championship success - on this evidence - still looks steep.
Ricky Hatton Tribute Inspires Local Rivalry Contest
In the supporting bout, Lyndon Arthur beat Rea by divided decision in a excellent local rivalry fight to win the European light-heavyweight belt.
The stadium grew hushed for a deeply poignant homage before the fight as a bell ceremony rang in remembrance of the city's native Ricky Hatton, who succumbed 46 years old in recently.
It was the premier televised fight night in the urban center since Hatton's death. As the concluding sound ended, the quiet transitioned to a shout of "there's only one Ricky Hatton".
The competition within the ring equaled the feeling. The eventual winner was sent to the canvas by a left hook directly to the jaw in the early round, rising shakily to his footing on the eight count.
But the Manchester United-red equipment of Arthur soon advanced again. On the opposite side, the opponent - in rival City blue - was marked up quickly, noticeable damage developing under his eye as the fighters exchanged punishing blows.
The challenger, twenty-seven, delivered effective strikes but the champion, thirty-four, responded in kind with effective uppercuts as the action rarely dropped over 12 rounds.
The victor edged the result with scoring tallies of 114-114, 115-113 and 115-112, but the two athletes were determined and courageous, all the qualities their hero Hatton stood for.
