British light heavyweight Buatsi made a winning yet underwhelming debut to life under fresh promotional backing with a points victory over Parker in the Manchester arena.
The Olympic medal winner's punch output seemingly secured him a majority decision in a competitive 10-round bout at the boxing arena.
But the challenger found success, delivering effective clean blows in a match where the styles failed to mesh, with frequent clinching spoiling the fight.
The scoring judges judged it 96-94 for to Buatsi, with the third a even score.
"It wasn't my greatest performance but what defines champions? They prevail," the victor said in the arena as he was greeted with disapproval from the spectators.
The British fighter bounced back after his initial pro loss - an epic battle with his previous opponent in February - to claim a twentieth professional win.
Several boxing experts believed the challenger, thirty-one, merited the victory but the contender experienced the second loss of his 28-match career.
Buatsi Earns Triumph in Uneventful Encounter
Buatsi's progress has plateaued in recent years through management issues and extended periods of lack of fights.
Once tipped as the future of UK boxing, he now finds himself trying to fulfil that early promise - possibly in what appears to be a final roll of the dice - under recent support.
He opened tentatively, with neither fighter ready to take risks in a tentative opening few rounds.
The challenger, whose only previous defeat came at super middleweight against his former opponent in 2022 after suffering a hand injury mid-fight, was competing in only his second bout at light-heavyweight.
By the fight's midpoint, Parker had kept it close, making life awkward for the favorite, who utilized a tight guard to edge the cleaner periods.
The audience's tolerance diminished during constant clinching, with Parker slipping to the canvas several times during clinches.
The underdog finished the stronger, but multiple periods were hard to judge. Nevertheless, former world champion the boxing analyst - working with the broadcast network - had it particularly wide for the challenger, awarding Buatsi just only one stanza.
The victor advances, but with the likes of power puncher David Benavidez, and Eastern European fighter Dmitry Bivol dominating the weight class, the road to world glory - judging by this showing - still appears challenging.
Ricky Hatton Homage Inspires Local Rivalry Battle
In the supporting bout, Arthur overcame Bradley Rea by split-decision in a excellent Manchester vs Manchester fight to capture the European light heavyweight championship.
The arena fell silent for a profoundly moving memorial before the fight as ten bells tolled in memory of Manchester's own Ricky Hatton, who succumbed at age 46 in last month.
It was the initial significant broadcast match card in the location since the passing of Hatton. As the last bell disappeared, the silence became a shout of "only one Ricky Hatton".
The competition inside the ropes equaled the sentiment. Arthur was knocked down by a powerful punch flush on the jaw in the initial stage, rising shakily to his position on the referee's count.
But the red-colored attire of the fighter soon came forward again. Across the ring, Rea - in opposing blue - was damaged quickly, significant bruising appearing under his orbital area as the fighters landed hard punches.
Rea, 27, delivered effective strikes but the champion, 34, responded in kind with powerful upward punches as the intensity hardly diminished over the full distance.
Arthur narrowly won the decision with scoring tallies of even score, 115-113 and wider gap, but the two athletes were determined and full of heart, everything their inspiration Hatton stood for.
