UK light-heavyweight Joshua Buatsi made a winning yet unimpressive start to life under fresh promotional backing with a points victory over Parker in the Manchester arena.
The Olympic bronze medallist's punch output seemingly secured him a majority decision in a close ten-round fight at the boxing arena.
But the challenger found success, delivering effective single shots in a contest where the styles never quite clicked, with frequent clinching disrupting the contest.
Two judges judged it 96-94 in favor to the winner, with the remaining official a 95-95 draw.
"It wasn't my finest performance but what do champions do? They win," Buatsi stated in the ringside as he was greeted with disapproval from the spectators.
The Londoner returned to winning ways after his initial pro loss - an memorable fight with his previous opponent in last winter - to claim a 20th pro success.
Various analysts felt Parker, thirty-one, deserved the decision but the Derbyshire fighter endured the second setback of his 28-match career.
The Champion Secures Triumph in Dull Encounter
His career development has slowed in recent years through promotional disputes and long spells of inactivity.
Once tipped as the rising talent of UK boxing, he now finds himself trying to fulfil that early promise - perhaps in what seems like a ultimate opportunity - under fresh management.
He began cautiously, with neither fighter willing to overcommit in a tentative early stages.
Parker, whose sole prior loss came at super-middleweight against his former opponent in 2022 after breaking his hand mid-fight, was competing in only his second fight at the higher weight class.
By the middle rounds, Parker had stayed in contention, creating difficulties for the favorite, who worked behind a protective stance to edge the more effective periods.
The crowd's patience diminished amid frequent holding, with Parker slipping to the canvas multiple occasions during close exchanges.
The underdog finished the stronger, but many rounds were hard to judge. Nevertheless, previous titleholder the boxing analyst - working with Dazn - had it particularly wide for the challenger, giving Buatsi just a single round.
Buatsi moves on, but with the presence of heavy hitter Benavidez, and Eastern European fighter Dmitry Bivol dominating the weight class, the journey to titles - on this evidence - still appears challenging.
Hatton Homage Inspires All-Manchester Fight
In the supporting bout, Lyndon Arthur overcame Rea by close verdict in a excellent local rivalry contest to secure the European light-heavyweight title.
The venue grew hushed for a extremely emotional homage ahead of the contest as ten bells sounded in remembrance of Manchester's own Ricky Hatton, who died at age 46 in September.
It was the initial significant broadcast match card in the urban center since the passing of Hatton. As the final chime disappeared, the quiet transitioned to a roar of "there's just one Ricky Hatton".
The fighting inside the ropes matched the feeling. The eventual winner was floored by a powerful punch directly to the face in the early round, getting up unsteadily to his position on the referee's count.
But the red-colored equipment of the fighter soon advanced again. On the opposite side, the opponent - in rival City blue - was marked up quickly, noticeable damage forming under his eye as the duo exchanged hard punches.
Rea, twenty-seven, connected with strong blows but the champion, 34, responded in kind with powerful upward punches as the intensity seldom decreased over twelve rounds.
The victor edged the decision with scoring tallies of even score, close margin and wider gap, but the two athletes were determined and courageous, exactly what their idol Hatton embodied.
