British light-heavyweight Buatsi made a winning yet unimpressive start to life under fresh promotional backing with a points victory over Zach Parker in the Manchester arena.
The Olympic bronze medallist's activity level likely gained him a majority decision in a close 10-round bout at the Manchester venue.
But Parker found success, connecting with powerful single shots in a fight where the styles never quite clicked, with frequent clinching marring the action.
The officials judged it 96-94 to the winner, with the remaining official a 95-95.
"It wasn't my best display but what defines champions? They succeed," Buatsi said in the ringside as he was greeted with disapproval from the spectators.
The British fighter got back to winning after his first professional defeat - an epic battle with his previous opponent in February - to claim a twentieth professional win.
Some ringside observers believed the challenger, 31, should have been awarded the victory but the Derbyshire fighter suffered the second defeat of his 28-bout career.
Buatsi Earns Win in Dull Affair
His career development has slowed in recent years through management issues and extended periods of inactivity.
Previously predicted as the future of UK boxing, he now is positioned trying to realize his potential - maybe in what seems like a final roll of the dice - under recent support.
He began cautiously, with neither fighter ready to take risks in a calculated initial rounds.
Parker, whose only previous defeat came at super-middleweight against John Ryder in 2022 after breaking his hand mid-fight, was competing in only his second fight at the higher weight class.
By the halfway stage, the underdog had made it competitive, making life awkward for Buatsi, who operated with a solid defense to narrowly win the more effective rounds.
The spectators' acceptance wore thin because of regular grabbing, with the challenger slipping to the canvas multiple occasions during grappling.
The underdog ended stronger, but many rounds were difficult to score. Nevertheless, previous titleholder the boxing analyst - commentating on Dazn - had it particularly wide for the challenger, awarding Buatsi just only one stanza.
Buatsi moves on, but with the caliber of power puncher David Benavidez, and Russian champion Dmitry Bivol dominating the weight class, the path to championship success - judging by this showing - still appears challenging.
Hatton Tribute Motivates Local Rivalry Battle
In the secondary fight, Arthur defeated Bradley Rea by split-decision in a outstanding local rivalry fight to secure the European light-heavyweight belt.
The arena became quiet for a profoundly moving memorial before the fight as ten bells sounded in remembrance of the city's native Ricky Hatton, who succumbed 46 years old in September.
It was the first major televised boxing event in the urban center since Hatton's passing. As the last bell faded, the quiet transitioned to a roar of "only one Hatton".
The action during the bout reflected the sentiment. Arthur was sent to the canvas by a significant blow directly to the jaw in the early round, standing uncertainly to his footing on the eight count.
But the Manchester United-red shorts of Arthur soon came forward again. From the other corner, Rea - in rival City blue - was injured early, significant bruising forming under his eye as the fighters exchanged punishing blows.
The challenger, 27, landed power punches but the champion, 34, fought fire with fire with effective uppercuts as the action hardly diminished over 12 rounds.
The victor edged the decision with official scores of even score, close margin and 115-112, but both fighters were determined and brave, exactly what their hero Hatton stood for.
