UK light heavyweight Buatsi earned a win yet unimpressive beginning to life under new promoters with a decision win over Zach Parker in Manchester.
The Olympic bronze medallist's activity level appeared to earn him a majority decision in a competitive 10-round bout at the Co-op Live Arena.
But Parker landed significant shots, landing some telling single shots in a contest where the techniques failed to mesh, with excessive holding marring the action.
The scoring judges judged it 96-94 to Buatsi, with the final judge a 95-95.
"It wasn't my greatest showing but what defines champions? They win," Buatsi commented in the arena as he was faced negative reactions from the crowd.
The Londoner got back to winning after his maiden career setback - an memorable fight with Callum Smith in February - to claim a twentieth professional win.
Various analysts felt the challenger, 31, should have been awarded the win but the Derbyshire fighter experienced the second setback of his 28-fight professional journey.
The Champion Secures Win in Uneventful Affair
Buatsi's progress has stalled in recent times through management issues and extended periods of inactivity.
Previously predicted as the rising talent of UK boxing, he now is positioned trying to realize his potential - possibly in what seems like a final roll of the dice - under recent support.
He began cautiously, with the two boxers ready to take risks in a calculated opening few rounds.
Parker, whose single earlier setback came at super middleweight against his former opponent in 2022 after suffering a hand injury mid-fight, 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 operated with a protective stance to barely take the cleaner rounds.
The spectators' acceptance decreased amid constant clinching, with Parker slipping to the canvas multiple occasions during clinches.
Parker closed well, but multiple periods were difficult to score. Nevertheless, former world champion Carl Frampton - commentating on Dazn - had it particularly wide for the challenger, awarding Buatsi just a single round.
Buatsi progresses, but with the likes of power puncher David Benavidez, and Russian star Dmitry Bivol leading the category, the journey to titles - on this evidence - still seems difficult.
Ricky Hatton Memorial Motivates Local Rivalry Battle
In the supporting bout, Lyndon Arthur beat Bradley Rea by close verdict in a excellent all-Manchester battle to capture the European light heavyweight championship.
The arena grew hushed for a deeply poignant tribute before the fight as ten bells rang in memory of Manchester's own Ricky Hatton, who succumbed aged 46 in last month.
It was the premier televised fight night in the location since Hatton's passing. As the last bell disappeared, the quiet gave way to a chant of "there's only one Ricky Hatton".
The fighting within the ring reflected the feeling. Arthur was floored by a significant blow flush on the jaw in the early round, getting up unsteadily to his feet on the eight count.
But the red-colored shorts of Arthur soon pressed ahead again. Across the ring, the opponent - in opposing blue - was marked up quickly, significant bruising appearing under his face as the fighters traded powerful shots.
Rea, 27, landed power punches but the champion, thirty-four, responded in kind with powerful upward punches as the action hardly diminished over the full distance.
The victor narrowly won the decision with judges scorecards of 114-114, close margin and wider gap, but each competitor were persistent and full of heart, all the qualities their inspiration the legend embodied.
