UK light heavyweight Buatsi secured a victory yet underwhelming start to his career under new promoters with a points victory over Zach Parker in the Manchester arena.
The Olympic bronze medallist's work rate seemingly secured him a split decision in a close ten-round contest at the Co-op Live Arena.
But Parker had his moments, delivering effective clean blows in a match where the styles never quite clicked, with frequent clinching spoiling the contest.
The scoring judges scored it 96-94 to Buatsi, with the remaining official a 95-95 draw.
"It wasn't my best performance but what defines champions? They win," Buatsi commented in the ringside as he was met by disapproval from the spectators.
The British fighter bounced back after his maiden career setback - an memorable fight with Callum Smith in February - to claim a 20th career victory.
Various analysts believed the challenger, thirty-one, deserved the win but the British boxer experienced the second setback of his 28-fight career.
The Champion Earns Win in Dull Encounter
His career development has stalled in the past few years through contract problems and extended periods of inactivity.
Earlier forecast as the next star of the British fight scene, he now is positioned trying to realize his potential - possibly in what seems like a final roll of the dice - under recent support.
He opened tentatively, with neither fighter willing to be aggressive in a tentative early stages.
The challenger, whose sole prior loss came at super-middleweight against John Ryder in 2022 after suffering a hand injury in the contest, was participating in his second fight at light-heavyweight.
By the fight's midpoint, the underdog had stayed in contention, making life awkward for Buatsi, who utilized a tight guard to edge the more effective rounds.
The audience's tolerance diminished during regular grabbing, with Parker going down multiple occasions during grappling.
Parker ended stronger, but multiple periods were difficult to score. However, ex-champion the boxing analyst - providing analysis for Dazn - had it strongly leaning for Parker, awarding Buatsi just only one stanza.
Buatsi moves on, but with the presence of hard hitter David Benavidez, and Eastern European fighter Bivol dominating the weight class, the road to world glory - based on this performance - still seems difficult.
Ricky Hatton Homage Fuels All-Manchester Fight
In the supporting bout, Lyndon Arthur defeated Rea by close verdict in a excellent local rivalry fight to secure the continental title.
The stadium became quiet for a deeply poignant homage ahead of the contest as 10 bells sounded in remembrance of Manchester's own Ricky Hatton, who succumbed 46 years old in last month.
It was the premier televised boxing event in the city since Hatton's death. As the final chime ended, the stillness gave way to a roar of "there's only one Hatton".
The fighting during the bout matched the emotion. Arthur was sent to the canvas by a powerful punch directly to the chin in the second round, rising shakily to his feet on the eight count.
But the Manchester United-red shorts of Arthur soon advanced again. Across the ring, the opponent - in rival City blue - was injured soon, noticeable damage forming under his orbital area as the duo exchanged hard punches.
Rea, twenty-seven, connected with strong blows but Arthur, thirty-four, matched the intensity with powerful upward punches as the pace seldom decreased over 12 rounds.
Arthur barely secured the decision with official scores of draw, 115-113 and wider gap, but both fighters were determined and brave, exactly what their idol the legend stood for.
