UK light heavyweight Buatsi made a winning yet disappointing debut to life under new promoters with a points victory over Zach Parker in the Manchester arena.
The Olympic medal winner's punch output likely gained him a majority decision in a tight ten-round bout at the Co-op Live Arena.
But the challenger landed significant shots, delivering effective clean blows in a fight where the techniques never quite clicked, with excessive holding disrupting the fight.
The officials judged it 96-94 in favor to the winner, with the final judge a 95-95.
"It wasn't my finest showing but how do champions respond? They prevail," Buatsi said in the ring as he was greeted with boos from the audience.
The Londoner got back to winning after his initial pro loss - an memorable fight with Callum Smith in last winter - to secure a 20th career victory.
Some ringside observers felt the challenger, 31, deserved the victory but the contender suffered the second defeat of his 28-match career.
Buatsi Claims Victory in Slow Affair
His career development has plateaued in the past few years through management issues and long spells of lack of fights.
Previously predicted as the future of the British fight scene, he now finds himself trying to realize his potential - possibly in what appears to be a last chance - under recent support.
He began cautiously, with both competitors prepared to take risks in a calculated opening few rounds.
The challenger, whose sole prior loss came at the lower weight class against John Ryder in 2022 after breaking his hand in the contest, was competing in only his second bout at the higher weight class.
By the middle rounds, the underdog had stayed in contention, causing problems for the favorite, who operated with a solid defense to narrowly win the more effective periods.
The spectators' acceptance wore thin because of regular grabbing, with the challenger slipping to the canvas several times during grappling.
The underdog finished the stronger, but multiple periods were difficult to score. However, former world champion the boxing analyst - working with Dazn - had it particularly wide for the challenger, awarding Buatsi just only one stanza.
The victor advances, but with the presence of heavy hitter David Benavidez, and Russian champion Dmitry Bivol dominating the weight class, the road to world glory - based on this performance - still looks steep.
Ricky Hatton Tribute Fuels Local Rivalry Contest
In the supporting bout, Lyndon Arthur beat Rea by divided decision in a excellent Manchester vs Manchester contest to capture the continental belt.
The venue fell silent for a deeply poignant memorial ahead of the contest as a bell ceremony rang in remembrance of Manchester's own Hatton, who died 46 years old in September.
It was the premier televised boxing event in the urban center since Hatton's death. As the last bell faded, the stillness transitioned to a chant of "there's just one Ricky Hatton".
The action inside the ropes reflected the sentiment. Arthur was sent to the canvas by a significant blow squarely on the face in the second round, getting up unsteadily to his feet on the referee's count.
But the red-colored attire of Arthur soon came forward again. From the other corner, Rea - in opposing blue - was injured quickly, significant bruising forming under his orbital area as the fighters landed hard punches.
The challenger, 27, landed power punches but the champion, thirty-four, responded in kind with powerful upward punches as the action seldom decreased over 12 rounds.
Arthur narrowly won the decision with judges scorecards of even score, narrow lead and 115-112, but both fighters were persistent and full of heart, exactly what their idol Hatton embodied.
