UK light-heavyweight Joshua Buatsi secured a victory yet disappointing 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 majority decision in a tight ten-round fight at the Manchester venue.
But the challenger had his moments, delivering effective individual punches in a fight where the techniques failed to mesh, with frequent clinching disrupting the contest.
The officials scored it 96-94 in favor to Buatsi, with the third a even score.
"It wasn't my best performance but what defines champions? They win," Buatsi stated in the ring as he was greeted with boos from the spectators.
The British fighter got back to winning after his maiden career setback - an thrilling contest with his previous opponent in February - to earn a twentieth professional win.
Some ringside observers felt the challenger, 31, should have been awarded the win but the British boxer suffered the second defeat of his 28-bout career.
The Champion Claims Triumph in Dull Match
Buatsi's progress has plateaued in the past few years through contract problems and long spells of inactivity.
Earlier forecast as the rising talent of the British fight scene, he now stands trying to fulfil that early promise - possibly in what feels like a last chance - under recent support.
He started carefully, with neither fighter willing to take risks in a calculated opening few rounds.
Parker, whose single earlier setback came at super middleweight against his former opponent in 2022 after suffering a hand injury during the bout, was competing in only his second fight at light-heavyweight.
By the fight's midpoint, the underdog had kept it close, making life awkward for Buatsi, who operated with a tight guard to narrowly win the cleaner stanzas.
The audience's tolerance wore thin because of constant clinching, with the challenger going down several times during grappling.
Parker closed well, but multiple periods were challenging to assess. Nevertheless, ex-champion Carl Frampton - providing analysis for Dazn - had it particularly wide for the challenger, scoring for Buatsi just only one stanza.
Buatsi advances, but with the presence of power puncher Benavidez, and Russian star Dmitry Bivol leading the category, the journey to titles - based on this performance - still seems difficult.
Hatton Homage Motivates Local Rivalry Battle
In the secondary fight, Arthur overcame Bradley Rea by split-decision in a excellent Manchester vs Manchester battle to capture the European light heavyweight title.
The stadium fell silent for a deeply poignant homage prior to the bout as ten bells rang in remembrance of Manchester's own Ricky Hatton, who succumbed 46 years old in last month.
It was the initial significant broadcast match card in the urban center since Hatton's death. As the concluding sound disappeared, the stillness transitioned to a chant of "there's only one Ricky Hatton".
The action within the ring matched the sentiment. Arthur was knocked down by a significant blow squarely on the jaw in the early round, rising shakily to his position on the referee's count.
But the traditional red shorts of the fighter soon pressed ahead again. From the other corner, Rea - in competitive blue - was injured quickly, significant bruising developing under his face as the pair exchanged powerful shots.
The challenger, 27, landed power punches but the champion, 34, fought fire with fire with effective uppercuts as the pace seldom decreased over the full distance.
Arthur edged the decision with judges scorecards of 114-114, close margin and 115-112, but each competitor were determined and brave, all the qualities their hero the legend embodied.
