UK light heavyweight Buatsi earned a win yet underwhelming debut to life under recent management with a decision win over Zach Parker in the Manchester arena.
The Olympic bronze medallist's punch output likely gained him a majority decision in a close ten-round fight at the boxing arena.
But the challenger landed significant shots, delivering effective single shots in a match where the techniques never quite clicked, with frequent clinching disrupting the contest.
Two judges had it 96-94 for to the winner, with the remaining official a 95-95.
"It wasn't my best display but how do champions respond? They succeed," the victor commented in the ring as he was greeted with negative reactions from the spectators.
The British fighter got back to winning after his initial pro loss - an thrilling contest with Callum Smith in February - to claim a twentieth professional win.
Some ringside observers believed Parker, 31, deserved the win but the British boxer suffered the second loss of his 28-fight professional journey.
Buatsi Claims Victory in Slow Match
His career development has plateaued in recent years through promotional disputes and extended periods of inactivity.
Once tipped as the future of UK boxing, he now stands trying to realize his potential - maybe in what seems like a last chance - under new promotional backing.
He opened tentatively, with both competitors ready to take risks in a tentative opening few rounds.
Parker, whose single earlier setback came at the lower weight class against his former opponent in 2022 after suffering a hand injury in the contest, was participating in his second bout at light-heavyweight.
By the middle rounds, the underdog had kept it close, creating difficulties for the favorite, who worked behind a tight guard to barely take the better rounds.
The spectators' acceptance wore thin amid regular grabbing, with the challenger slipping to the canvas multiple occasions during clinches.
Parker finished the stronger, but multiple periods were challenging to assess. Although, previous titleholder the boxing analyst - working with Dazn - had it significantly in favor for Parker, giving Buatsi just a single round.
The victor progresses, but with the presence of hard hitter Benavidez, and Russian star Dmitry Bivol leading the category, the path to championship success - on this evidence - still looks steep.
Ricky Hatton Homage Inspires Local Rivalry Contest
In the co-main event, Arthur overcame Rea by close verdict in a terrific Manchester vs Manchester fight to capture the European light heavyweight championship.
The venue grew hushed for a profoundly moving homage before the fight as 10 bells rang in memory of local hero Ricky Hatton, who succumbed 46 years old in last month.
It was the first major televised boxing event in the city since the passing of Hatton. As the concluding sound ended, the stillness became a chant of "there's just one Ricky Hatton".
The competition during the bout matched the feeling. Arthur was sent to the canvas by a significant blow directly to the jaw in the second round, standing uncertainly to his position on the count of eight.
But the Manchester United-red shorts of Arthur soon came forward again. From the other corner, Rea - in opposing blue - was damaged soon, significant bruising developing under his eye as the duo exchanged punishing blows.
The challenger, 27, connected with strong blows but the champion, 34, matched the intensity with powerful upward punches as the pace hardly diminished over twelve rounds.
The victor barely secured the decision with official scores of even score, 115-113 and 115-112, but both fighters were determined and courageous, everything their hero the legend embodied.
