UK light heavyweight Joshua Buatsi secured a victory yet disappointing start to his career under fresh promotional backing with a decision win over Parker in the Manchester arena.
The Olympic bronze medallist's activity level seemingly secured him a split decision in a competitive ten-round fight at the boxing arena.
But Parker landed significant shots, connecting with powerful individual punches in a fight where the techniques didn't complement each other, with frequent clinching spoiling the action.
The officials scored it 96-94 in favor to the winner, with the final judge a even score.
"It wasn't my best showing but what do champions do? They win," Buatsi stated in the ringside as he was greeted with negative reactions from the spectators.
The Londoner bounced back after his first professional defeat - an epic battle with Callum Smith in February - to earn a 20th pro success.
Several boxing experts thought the challenger, 31, deserved the victory but the Derbyshire fighter endured the second setback of his 28-fight professional journey.
Buatsi Secures Win in Slow Encounter
The fighter's advancement has stalled in the past few years through management issues and extended periods of inactivity.
Once tipped as the future of the British fight scene, he now finds himself trying to achieve expectations - maybe in what seems like a ultimate opportunity - under fresh management.
He began cautiously, with the two boxers ready to take risks in a cagey early stages.
Parker, whose single earlier setback came at super middleweight against John Ryder in 2022 after damaging his hand mid-fight, was participating in his second appearance at light heavyweight.
By the middle rounds, Parker had made it competitive, making life awkward for the favorite, who worked behind a solid defense to edge the cleaner rounds.
The audience's tolerance diminished because of constant clinching, with Parker slipping to the canvas various instances during grappling.
The underdog closed well, but many rounds were challenging to assess. Nevertheless, former world champion the boxing analyst - working with Dazn - had it significantly in favor for Parker, giving Buatsi just one round.
The victor advances, but with the likes of hard hitter David Benavidez, and Russian star Bivol ruling the division, the road to world glory - judging by this showing - still appears challenging.
Hatton Tribute Fuels All-Manchester Battle
In the secondary fight, Lyndon Arthur beat Rea by divided decision in a excellent Manchester vs Manchester battle to capture the European light-heavyweight belt.
The venue grew hushed for a extremely emotional memorial prior to the bout as ten bells tolled in remembrance of local hero Ricky Hatton, who succumbed aged 46 in last month.
It was the initial significant broadcast boxing event in the urban center since Hatton's passing. As the concluding sound disappeared, the stillness became a shout of "there's just one Hatton".
The action during the bout equaled the feeling. Arthur was floored by a significant blow directly to the chin in the early round, getting up unsteadily to his feet on the eight count.
But the red-colored equipment of Arthur soon pressed ahead again. On the opposite side, Rea - in opposing blue - was injured soon, significant bruising forming under his orbital area as the duo landed hard punches.
Rea, 27, connected with strong blows but the champion, 34, matched the intensity with effective uppercuts as the action seldom decreased over twelve rounds.
Arthur narrowly won the verdict with scoring tallies of even score, 115-113 and wider gap, but each competitor were relentless and full of heart, all the qualities their hero Hatton stood for.
