British light heavyweight Buatsi made a winning yet unimpressive start to life under fresh promotional backing with a decision win over Zach Parker in Manchester.
The Olympic bronze medallist's work rate appeared to earn him a split decision in a close 10-round fight at the Co-op Live Arena.
But the challenger found success, delivering effective clean blows in a contest where the techniques failed to mesh, with constant grabbing marring the action.
The scoring judges scored it 96-94 in favor to Buatsi, with the third a 95-95.
"It wasn't my greatest showing but how do champions respond? They prevail," the victor said in the ringside as he was met by boos from the audience.
The Londoner bounced back after his maiden career setback - an memorable fight with his previous opponent in last winter - to earn a twentieth professional win.
Some ringside observers felt Parker, 31, merited the win but the contender endured the second setback of his 28-match career.
Buatsi Claims Victory in Dull Match
Buatsi's progress has slowed in recent years through management issues and long spells of inactivity.
Earlier forecast as the rising talent of British boxing, he now stands trying to fulfil that early promise - possibly in what feels like a last chance - under new promotional backing.
He started carefully, with both competitors prepared to overcommit in a tentative opening few rounds.
The challenger, whose single earlier setback came at super-middleweight against his former opponent in 2022 after suffering a hand injury during the bout, was making just his second bout at light-heavyweight.
By the middle rounds, the underdog had stayed in contention, creating difficulties for the favorite, who utilized a tight guard to barely take the better stanzas.
The crowd's patience wore thin amid constant clinching, with Parker slipping to the canvas various instances during clinches.
Parker finished the stronger, but multiple periods were hard to judge. Nevertheless, former world champion Carl Frampton - working with the broadcast network - had it strongly leaning for the challenger, scoring for Buatsi just one round.
The victor advances, but with the likes of power puncher David Benavidez, and Russian champion Bivol leading the category, the road to world glory - judging by this showing - still seems difficult.
Ricky Hatton Memorial Inspires Local Rivalry Fight
In the secondary fight, Arthur defeated Rea by close verdict in a terrific local rivalry contest to secure the European light-heavyweight title.
The arena fell silent for a profoundly moving homage before the fight as 10 bells rang in remembrance of Manchester's own Hatton, who passed away aged 46 in recently.
It was the premier televised match card in the location since the passing of Hatton. As the concluding sound faded, the quiet transitioned to a shout of "only one Ricky Hatton".
The action inside the ropes reflected the feeling. The eventual winner was knocked down by a left hook flush on the chin in the early round, standing uncertainly to his footing on the referee's count.
But the traditional red equipment of Arthur soon pressed ahead again. Across the ring, the opponent - in rival City blue - was marked up early, significant bruising forming under his face as the fighters traded powerful shots.
The challenger, 27, landed power punches but Arthur, 34, responded in kind with powerful upward punches as the intensity hardly diminished over twelve rounds.
Arthur narrowly won the result with scoring tallies of 114-114, close margin and wider gap, but both fighters were persistent and courageous, everything their inspiration Hatton stood for.
