British light heavyweight Joshua Buatsi earned a win yet underwhelming start to his career under recent management with a unanimous decision over Parker in Manchester.
The Olympic medal winner's punch output seemingly secured him a judges' verdict in a competitive 10-round fight at the boxing arena.
But the challenger landed significant shots, connecting with powerful individual punches in a fight where the styles never quite clicked, with constant grabbing disrupting the contest.
The officials judged it 96-94 for to the winner, with the final judge a even score.
"It wasn't my greatest display but what do champions do? They win," Buatsi commented in the ring as he was faced boos from the spectators.
The British fighter returned to winning ways after his maiden career setback - an memorable fight with Callum Smith in last winter - to claim a twentieth professional win.
Several boxing experts felt Parker, 31, should have been awarded the win but the Derbyshire fighter suffered the second setback of his 28-fight career.
Buatsi Earns Victory in Dull Match
The fighter's advancement has plateaued in recent years through management issues and long spells of inactivity.
Previously predicted as the rising talent of British boxing, he now stands trying to achieve expectations - maybe in what appears to be a last chance - under new promotional backing.
He started carefully, with the two boxers ready to be aggressive in a tentative initial rounds.
The challenger, whose sole prior loss came at super-middleweight against his former opponent in 2022 after damaging his hand mid-fight, was competing in only his second bout at light-heavyweight.
By the fight's midpoint, the underdog had stayed in contention, creating difficulties for Buatsi, who utilized a protective stance to narrowly win the better stanzas.
The spectators' acceptance wore thin because of regular grabbing, with Parker falling to the floor various instances during grappling.
Parker finished the stronger, but many rounds were difficult to score. Although, ex-champion Carl Frampton - providing analysis for Dazn - had it significantly in favor for the challenger, giving Buatsi just only one stanza.
Buatsi progresses, but with the likes of heavy hitter David Benavidez, and Eastern European fighter Dmitry Bivol leading the category, the path to championship success - based on this performance - still looks steep.
Ricky Hatton Homage Motivates Local Rivalry Contest
In the secondary fight, Arthur defeated Rea by close verdict in a outstanding Manchester vs Manchester fight to capture the European light-heavyweight title.
The stadium fell silent for a profoundly moving tribute before the fight as a bell ceremony tolled in remembrance of Manchester's own Hatton, who passed away aged 46 in last month.
It was the first major televised match card in the location since Hatton's death. As the final chime faded, the stillness became a shout of "there's only one Ricky Hatton".
The action during the bout reflected the sentiment. Arthur was knocked down by a powerful punch squarely on the jaw in the initial stage, standing uncertainly to his footing on the referee's count.
But the traditional red shorts of the fighter soon came forward again. From the other corner, the opponent - in opposing blue - was marked up early, significant bruising forming under his eye as the fighters traded punishing blows.
Rea, 27, landed power punches but the champion, thirty-four, matched the intensity with effective uppercuts as the intensity rarely dropped over twelve rounds.
The victor barely secured the result with scoring tallies of draw, 115-113 and 115-112, but each competitor were determined and full of heart, exactly what their idol the legend embodied.
