British light heavyweight Joshua Buatsi secured a victory yet disappointing beginning to life under fresh promotional backing 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 competitive 10-round contest at the Co-op Live Arena.
But the challenger had his moments, delivering effective clean blows in a contest where the techniques never quite clicked, with constant grabbing marring the contest.
The scoring judges had it 96-94 to the winner, with the final judge a 95-95 draw.
"It wasn't my best performance but how do champions respond? They succeed," Buatsi commented in the arena as he was greeted with negative reactions from the crowd.
The British fighter got back to winning after his initial pro loss - an memorable fight with his previous opponent in February - to earn a twentieth professional win.
Several boxing experts thought Parker, thirty-one, merited the win but the British boxer experienced the second loss of his 28-match career.
Buatsi Earns Victory in Dull Match
Buatsi's progress has plateaued in recent years through promotional disputes and long spells of inactivity.
Previously predicted as the rising talent of UK boxing, he now finds himself trying to achieve expectations - perhaps in what feels like a final roll of the dice - under fresh management.
He started carefully, with both competitors prepared to take risks in a calculated early stages.
The challenger, whose only previous defeat came at super middleweight against his former opponent in 2022 after breaking his hand in the contest, was participating in his second bout at light-heavyweight.
By the middle rounds, the underdog had stayed in contention, causing problems for Buatsi, who utilized a protective stance to narrowly win the better rounds.
The audience's tolerance decreased because of regular grabbing, with the challenger falling to the floor several times during clinches.
The underdog finished the stronger, but many rounds were hard to judge. Although, former world champion Carl Frampton - working with the broadcast network - had it strongly leaning for the challenger, scoring for Buatsi just only one stanza.
Buatsi advances, but with the caliber of hard hitter Benavidez, and Russian champion Bivol leading the category, the path to championship success - judging by this showing - still appears challenging.
Hatton Memorial Motivates Manchester Derby Battle
In the co-main event, Arthur overcame Rea by split-decision in a outstanding Manchester vs Manchester fight to secure the European light-heavyweight title.
The stadium fell silent for a deeply poignant homage before the fight as ten bells tolled in honor of Manchester's own Hatton, who died 46 years old in recently.
It was the premier televised boxing event in the urban center since Hatton's passing. As the concluding sound faded, the stillness gave way to a roar of "there's just one Hatton".
The action within the ring equaled the emotion. The eventual winner was floored by a powerful punch flush on the jaw in the second round, getting up unsteadily to his position on the count of eight.
But the red-colored equipment of the fighter soon came forward again. From the other corner, the opponent - in competitive blue - was marked up early, noticeable damage forming under his face as the pair landed hard punches.
Rea, twenty-seven, landed power punches but the champion, 34, responded in kind with powerful upward punches as the intensity hardly diminished over twelve rounds.
Arthur edged the verdict with judges scorecards of 114-114, narrow lead and clearer margin, but each competitor were determined and courageous, everything their inspiration the legend represented.
