British light-heavyweight Joshua Buatsi made a winning yet underwhelming start to his career under recent management with a unanimous decision over Parker in the Manchester arena.
The Olympic bronze medallist's activity level seemingly secured him a split decision in a close 10-round fight at the boxing arena.
But Parker found success, connecting with powerful single shots in a contest where the approaches didn't complement each other, with constant grabbing spoiling the contest.
The officials judged it 96-94 in favor to the winner, with the third a 95-95.
"It wasn't my best showing but what defines champions? They succeed," the victor commented in the arena as he was met by negative reactions from the audience.
The Londoner returned to winning ways after his maiden career setback - an thrilling contest with his previous opponent in last winter - to claim a 20th career victory.
Several boxing experts felt the challenger, 31, deserved the victory but the Derbyshire fighter endured the second defeat of his 28-match professional journey.
Buatsi Secures Victory in Dull Match
His career development has slowed in the past few years through management issues and long spells of inactivity.
Previously predicted as the future of the British fight scene, he now finds himself trying to fulfil that early promise - perhaps in what feels like a final roll of the dice - under fresh management.
He started carefully, with the two boxers willing to be aggressive in a cagey initial rounds.
Parker, whose only previous defeat came at super-middleweight against John Ryder in two years ago after damaging his hand during the bout, was participating in his second bout at light-heavyweight.
By the middle rounds, Parker had stayed in contention, making life awkward for Buatsi, who operated with a protective stance to edge the better rounds.
The spectators' acceptance diminished during constant clinching, with the challenger falling to the floor several times during clinches.
The underdog closed well, but many rounds were hard to judge. Nevertheless, ex-champion Carl Frampton - providing analysis for the broadcast network - had it particularly wide for Parker, awarding Buatsi just only one stanza.
Buatsi progresses, but with the likes of power puncher David Benavidez, and Russian champion Dmitry Bivol leading the category, the path to championship success - judging by this showing - still seems difficult.
Hatton Homage Fuels All-Manchester Battle
In the supporting bout, Arthur beat Bradley Rea by divided decision in a terrific Manchester vs Manchester contest to capture the European light heavyweight title.
The venue fell silent for a extremely emotional memorial ahead of the contest as ten bells rang in remembrance of Manchester's own Hatton, who succumbed at age 46 in last month.
It was the first major televised boxing event in the city since Hatton's death. As the concluding sound faded, the stillness gave way to a roar of "there's only one Hatton".
The action during the bout reflected the emotion. The eventual winner was floored by a significant blow directly to the face in the initial stage, rising shakily to his footing on the eight count.
But the red-colored attire of Arthur soon advanced again. Across the ring, Rea - in rival City blue - was injured early, noticeable damage developing under his eye as the fighters exchanged punishing blows.
Rea, 27, delivered effective strikes but the champion, thirty-four, responded in kind with effective uppercuts as the intensity hardly diminished over the full distance.
Arthur edged the result with judges scorecards of draw, narrow lead and wider gap, but the two athletes were determined and full of heart, everything their hero the legend embodied.
