British light heavyweight Joshua Buatsi secured a victory yet underwhelming debut to his career under new promoters with a decision win over Parker in Manchester.
The Olympic bronze medallist's activity level likely gained him a split decision in a close ten-round contest at the boxing arena.
But the challenger had his moments, delivering effective single shots in a match where the approaches failed to mesh, with constant grabbing disrupting the contest.
Two judges scored it 96-94 in favor to Buatsi, with the final judge a even score.
"It wasn't my best performance but what do champions do? They succeed," the victor said in the ring as he was greeted with negative reactions from the crowd.
The British fighter got back to winning after his first professional defeat - an memorable fight with his previous opponent in last winter - to earn a 20th pro success.
Various analysts believed the challenger, thirty-one, should have been awarded the victory but the contender experienced the second loss of his 28-fight professional journey.
Buatsi Secures Victory in Slow Match
Buatsi's progress has slowed in the past few years through promotional disputes and long spells of inactivity.
Once tipped as the rising talent of the British fight scene, he now stands trying to achieve expectations - maybe in what appears to be a ultimate opportunity - under new promotional backing.
He started carefully, with the two boxers willing to take risks in a cagey early stages.
Parker, whose only previous defeat came at super-middleweight against his former opponent in 2022 after damaging his hand in the contest, was participating in his second appearance at the higher weight class.
By the fight's midpoint, the underdog had stayed in contention, creating difficulties for the favorite, who worked behind a protective stance to barely take the better periods.
The spectators' acceptance wore thin because of regular grabbing, with Parker falling to the floor multiple occasions during clinches.
Parker ended stronger, but several stanzas were difficult to score. Nevertheless, former world champion Carl Frampton - providing analysis for Dazn - had it strongly leaning for the challenger, giving Buatsi just a single round.
Buatsi advances, but with the caliber of heavy hitter David Benavidez, and Russian star Dmitry Bivol ruling the division, the journey to titles - based on this performance - still looks steep.
Ricky Hatton Memorial Fuels Local Rivalry Battle
In the secondary fight, Arthur overcame Rea by split-decision in a terrific local rivalry contest to win the continental belt.
The venue grew hushed for a deeply poignant tribute before the fight as ten bells sounded in honor of local hero Hatton, who succumbed 46 years old in last month.
It was the first major televised fight night in the city since the passing of Hatton. As the concluding sound disappeared, the quiet transitioned to a chant of "there's only one Ricky Hatton".
The action during the bout reflected the sentiment. Arthur was sent to the canvas by a significant blow flush on the jaw in the second round, getting up unsteadily to his feet on the eight count.
But the red-colored attire of the fighter soon advanced again. From the other corner, the opponent - in opposing blue - was injured early, significant bruising appearing under his orbital area as the pair exchanged powerful shots.
Rea, twenty-seven, connected with strong blows but the champion, 34, responded in kind with stinging uppercuts as the action hardly diminished over the full distance.
The victor edged the verdict with scoring tallies of draw, 115-113 and wider gap, but each competitor were relentless and full of heart, everything their idol the legend represented.
