British light-heavyweight Joshua Buatsi secured a victory yet unimpressive beginning to life under recent management with a points victory over Parker in the Manchester arena.
The Olympic bronze medallist's activity level seemingly secured him a judges' verdict in a tight 10-round bout at the boxing arena.
But Parker found success, landing some telling individual punches in a match where the techniques failed to mesh, with constant grabbing spoiling the contest.
Two judges judged it 96-94 for to the winner, with the final judge a 95-95.
"It wasn't my finest showing but how do champions respond? They prevail," Buatsi stated in the arena as he was met by disapproval from the crowd.
The Londoner got back to winning after his maiden career setback - an thrilling contest with his previous opponent in last winter - to claim a 20th career victory.
Various analysts believed Parker, 31, merited the win but the contender suffered the second defeat of his 28-bout professional journey.
Buatsi Earns Win in Slow Affair
Buatsi's progress has plateaued in the past few years through contract problems and extended periods of inactivity.
Previously predicted as the next star of UK boxing, he now stands trying to achieve expectations - perhaps in what seems like a ultimate opportunity - under new promotional backing.
He began cautiously, with neither fighter prepared to be aggressive in a tentative opening few rounds.
The challenger, whose only previous defeat came at super-middleweight against his former opponent in 2022 after damaging his hand during the bout, was competing in only his second bout at the higher weight class.
By the halfway stage, Parker had stayed in contention, making life awkward for the favorite, who worked behind a tight guard to narrowly win the better stanzas.
The spectators' acceptance decreased amid constant clinching, with Parker falling to the floor various instances during grappling.
Parker finished the stronger, but multiple periods were challenging to assess. However, former world champion Carl Frampton - providing analysis for Dazn - had it particularly wide for Parker, awarding Buatsi just one round.
The victor progresses, but with the presence of heavy hitter Benavidez, and Russian star Dmitry Bivol ruling the division, the road to world glory - based on this performance - still looks steep.
Hatton Memorial Fuels Local Rivalry Battle
In the secondary fight, Lyndon Arthur beat Bradley Rea by split-decision in a terrific Manchester vs Manchester battle to secure the European light heavyweight title.
The stadium grew hushed for a deeply poignant memorial ahead of the contest as a bell ceremony sounded in memory of the city's native Ricky Hatton, who died 46 years old in recently.
It was the initial significant broadcast boxing event in the location since Hatton's death. As the concluding sound ended, the silence gave way to a shout of "there's only one Hatton".
The action inside the ropes matched the emotion. The eventual winner was sent to the canvas by a powerful punch directly to the chin in the second round, standing uncertainly to his position on the count of eight.
But the Manchester United-red attire of Arthur soon pressed ahead again. From the other corner, Rea - in opposing blue - was marked up soon, heavy swelling developing under his face as the pair landed powerful shots.
The challenger, twenty-seven, delivered effective strikes but the champion, 34, fought fire with fire with effective uppercuts as the intensity hardly diminished over twelve rounds.
Arthur edged the verdict with judges scorecards of draw, close margin and 115-112, but the two athletes were determined and full of heart, everything their inspiration the legend stood for.
