UK light heavyweight Joshua Buatsi secured a victory yet disappointing debut to life under recent management with a decision win over Parker in the Manchester arena.
The Olympic bronze medallist's activity level seemingly secured him a majority decision in a tight 10-round fight at the boxing arena.
But the challenger found success, landing some telling clean blows in a match where the techniques never quite clicked, with constant grabbing spoiling the fight.
The scoring judges judged it 96-94 to Buatsi, with the final judge a even score.
"It wasn't my best display but what do champions do? They prevail," the victor commented in the arena as he was faced disapproval from the audience.
The Londoner returned to winning ways after his maiden career setback - an epic battle with his previous opponent in last winter - to earn a 20th career victory.
Various analysts believed the challenger, thirty-one, deserved the win but the contender suffered the second loss of his 28-bout career.
Buatsi Secures Victory in Dull Encounter
His career development has slowed in recent years through promotional disputes and extended periods of inactivity.
Earlier forecast as the rising talent of UK boxing, he now stands trying to realize his potential - possibly in what appears to be a final roll of the dice - under new promotional backing.
He began cautiously, with neither fighter ready to overcommit in a calculated initial rounds.
The challenger, whose single earlier setback came at super-middleweight against his former opponent in 2022 after breaking his hand in the contest, was competing in only his second bout at light-heavyweight.
By the halfway stage, the underdog had stayed in contention, making life awkward for Buatsi, who operated with a tight guard to narrowly win the better stanzas.
The audience's tolerance decreased because of frequent holding, with the challenger slipping to the canvas several times during close exchanges.
The underdog closed well, but multiple periods were hard to judge. Although, previous titleholder the boxing analyst - commentating on Dazn - had it strongly leaning for Parker, giving Buatsi just one round.
Buatsi progresses, but with the caliber of hard hitter Benavidez, and Russian champion Dmitry Bivol ruling the division, the journey to titles - on this evidence - still seems difficult.
Ricky Hatton Homage Fuels Manchester Derby Battle
In the co-main event, Arthur defeated Rea by close verdict in a excellent local rivalry battle to capture the European light heavyweight championship.
The stadium fell silent for a deeply poignant memorial ahead of the contest as 10 bells rang in honor of Manchester's own Hatton, who passed away at age 46 in September.
It was the premier televised match card in the urban center since Hatton's death. As the concluding sound faded, the quiet gave way to a roar of "there's only one Ricky Hatton".
The competition within the ring reflected the emotion. Arthur was knocked down by a powerful punch flush on the face in the early round, standing uncertainly to his position on the referee's count.
But the red-colored shorts of the fighter soon advanced again. Across the ring, Rea - in competitive blue - was marked up quickly, noticeable damage developing under his face as the pair traded powerful shots.
Rea, twenty-seven, connected with strong blows but the champion, 34, responded in kind with powerful upward punches as the action hardly diminished over twelve rounds.
Arthur narrowly won the decision with scoring tallies of draw, narrow lead and wider gap, but both fighters were determined and full of heart, all the qualities their hero Hatton represented.
