British light-heavyweight Joshua Buatsi secured a victory yet disappointing debut to life under fresh promotional backing with a decision win over Parker in the Manchester arena.
The Olympic medal winner's activity level appeared to earn him a split decision in a tight ten-round bout at the boxing arena.
But Parker landed significant shots, landing some telling clean blows in a contest where the styles didn't complement each other, with frequent clinching marring the action.
Two judges scored it 96-94 to the winner, with the remaining official a even score.
"It wasn't my greatest performance but what do champions do? They win," Buatsi commented in the arena as he was greeted with disapproval from the audience.
The Londoner got back to winning after his initial pro loss - an memorable fight with Callum Smith in February - to claim a twentieth professional win.
Various analysts believed the challenger, thirty-one, should have been awarded the victory but the contender suffered the second loss of his 28-fight professional journey.
Buatsi Claims Victory in Uneventful Encounter
His career development has stalled in the past few years through management issues and extended periods of inactivity.
Earlier forecast as the future of UK boxing, he now finds himself trying to achieve expectations - possibly in what feels like a last chance - under recent support.
He started carefully, with the two boxers willing to be aggressive in a cagey opening few rounds.
The challenger, whose single earlier setback came at super middleweight against his former opponent in 2022 after damaging his hand during the bout, was making just his second appearance at light-heavyweight.
By the fight's midpoint, the underdog had kept it close, causing problems for the favorite, who operated with a tight guard to barely take the better stanzas.
The crowd's patience decreased during constant clinching, with the challenger falling to the floor several times during close exchanges.
The underdog finished the stronger, but many rounds were challenging to assess. Although, previous titleholder Carl Frampton - commentating on Dazn - had it particularly wide for the challenger, scoring for Buatsi just only one stanza.
The victor moves on, but with the presence of heavy hitter David Benavidez, and Russian star Bivol dominating the weight class, the road to world glory - based on this performance - still appears challenging.
Ricky Hatton Memorial Fuels Manchester Derby Battle
In the co-main event, Lyndon Arthur defeated Bradley Rea by close verdict in a excellent Manchester vs Manchester battle to capture the continental championship.
The stadium fell silent for a profoundly moving memorial ahead of the contest as a bell ceremony tolled in memory of the city's native Ricky Hatton, who succumbed aged 46 in recently.
It was the premier televised boxing event in the city since Hatton's passing. As the concluding sound ended, the quiet became a shout of "only one Ricky Hatton".
The competition inside the ropes reflected the feeling. Arthur was knocked down by a powerful punch squarely on the chin in the second round, rising shakily to his position on the referee's count.
But the traditional red shorts of the fighter soon advanced again. Across the ring, the opponent - in competitive blue - was damaged early, noticeable damage developing under his orbital area as the duo exchanged hard punches.
Rea, 27, connected with strong blows but the champion, thirty-four, matched the intensity with stinging uppercuts as the action seldom decreased over 12 rounds.
Arthur edged the result with scoring tallies of 114-114, 115-113 and wider gap, but both fighters were relentless and full of heart, everything their inspiration the legend represented.
