UK light heavyweight Joshua Buatsi secured a victory yet unimpressive beginning to his career under recent management with a points victory over Parker in the Manchester arena.
The Olympic medal winner's work rate likely gained him a judges' verdict in a close ten-round bout at the boxing arena.
But Parker found success, landing some telling clean blows in a match where the styles failed to mesh, with excessive holding marring the fight.
The scoring judges scored it 96-94 to the winner, with the third a even score.
"It wasn't my finest showing but what defines champions? They succeed," Buatsi said in the ringside as he was met by boos from the audience.
The British fighter got back to winning after his first professional defeat - an thrilling contest with Callum Smith in February - to earn a 20th pro success.
Various analysts felt the challenger, 31, merited the win but the contender suffered the second loss of his 28-match professional journey.
His career development has stalled in recent times through promotional disputes and extended periods of inactivity.
Once tipped as the next star of British boxing, he now finds himself trying to realize his potential - possibly in what seems like a ultimate opportunity - under fresh management.
He started carefully, with the two boxers ready to overcommit in a cagey opening few rounds.
The challenger, whose single earlier setback came at super middleweight against John Ryder in two years ago after damaging his hand during the bout, was competing in only his second bout at light-heavyweight.
By the middle rounds, Parker had made it competitive, creating difficulties for the favorite, who operated with a tight guard to edge the more effective stanzas.
The spectators' acceptance wore thin during regular grabbing, with the challenger going down multiple occasions during grappling.
Parker closed well, but many rounds were hard to judge. However, previous titleholder the boxing analyst - working with Dazn - had it strongly leaning for Parker, giving Buatsi just only one stanza.
The victor progresses, but with the presence of hard hitter Benavidez, and Russian champion Dmitry Bivol ruling the division, the journey to titles - based on this performance - still seems difficult.
In the secondary fight, Arthur defeated Rea by close verdict in a outstanding local rivalry contest to secure the European light-heavyweight championship.
The venue fell silent for a profoundly moving tribute ahead of the contest as ten bells tolled in memory of local hero Hatton, who died 46 years old in September.
It was the first major televised fight night in the city since Hatton's death. As the concluding sound faded, the silence gave way to a chant of "only one Hatton".
The competition within the ring matched the feeling. The eventual winner was floored by a powerful punch flush on the chin in the initial stage, standing uncertainly to his footing on the referee's count.
But the traditional red shorts of Arthur soon advanced again. On the opposite side, the opponent - in rival City blue - was injured early, noticeable damage forming under his face as the duo exchanged punishing blows.
Rea, twenty-seven, connected with strong blows but Arthur, thirty-four, fought fire with fire with stinging uppercuts as the intensity seldom decreased over twelve rounds.
Arthur edged the verdict with scoring tallies of draw, narrow lead and clearer margin, but both fighters were determined and courageous, exactly what their idol Hatton stood for.
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