British light-heavyweight Joshua Buatsi earned a win yet disappointing debut to his career under recent management with a points victory over Parker in the Manchester arena.
The Olympic bronze medallist's work rate appeared to earn him a majority decision in a competitive ten-round contest at the boxing arena.
But the challenger landed significant shots, landing some telling single shots in a match where the techniques didn't complement each other, with excessive holding marring the action.
Two judges scored it 96-94 for to Buatsi, with the final judge a even score.
"It wasn't my finest display but what defines champions? They win," the victor stated in the ring as he was met by negative reactions from the crowd.
The Londoner bounced back after his maiden career setback - an thrilling contest with Callum Smith in February - to claim a 20th career victory.
Various analysts believed the challenger, 31, should have been awarded the decision but the contender experienced the second loss of his 28-bout professional journey.
Buatsi Earns Triumph in Uneventful Match
The fighter's advancement has slowed in recent times through promotional disputes and long spells of inactivity.
Earlier forecast as the future of the British fight scene, he now stands trying to fulfil that early promise - maybe in what feels like a final roll of the dice - under new promotional backing.
He opened tentatively, with the two boxers prepared to be aggressive in a tentative early stages.
The challenger, whose sole prior loss came at super-middleweight against John Ryder in 2022 after suffering a hand injury in the contest, was competing in only his second fight at light-heavyweight.
By the fight's midpoint, Parker had made it competitive, making life awkward for Buatsi, who worked behind a tight guard to edge the more effective rounds.
The audience's tolerance decreased because of constant clinching, with the challenger slipping to the canvas several times during grappling.
The underdog closed well, but multiple periods were difficult to score. However, previous titleholder the boxing analyst - commentating on the broadcast network - had it significantly in favor for the challenger, giving Buatsi just one round.
Buatsi moves on, but with the caliber of power puncher Benavidez, and Russian star Dmitry Bivol ruling the division, the path to championship success - on this evidence - still appears challenging.
Ricky Hatton Tribute Fuels Manchester Derby Battle
In the co-main event, Arthur overcame Bradley Rea by close verdict in a outstanding all-Manchester fight to secure the European light-heavyweight championship.
The stadium fell silent for a deeply poignant tribute before the fight as 10 bells rang in honor of local hero Ricky Hatton, who succumbed 46 years old in September.
It was the premier televised fight night in the city since the passing of Hatton. As the final chime disappeared, the stillness gave way to a chant of "only one Ricky Hatton".
The fighting within the ring equaled the feeling. The eventual winner was sent to the canvas by a left hook directly to the jaw in the second round, rising shakily to his footing on the referee's count.
But the traditional red shorts of Arthur soon pressed ahead again. Across the ring, the opponent - in competitive blue - was marked up early, noticeable damage developing under his face as the duo exchanged powerful shots.
Rea, twenty-seven, landed power punches but Arthur, 34, fought fire with fire with stinging uppercuts as the action seldom decreased over the full distance.
Arthur edged the verdict with official scores of 114-114, close margin and 115-112, but the two athletes were determined and courageous, exactly what their idol Hatton represented.
