UK light heavyweight Buatsi made a winning yet disappointing start to his career under new promoters with a points victory over Zach Parker in the Manchester arena.
The Olympic bronze medallist's activity level seemingly secured him a judges' verdict in a competitive 10-round fight at the boxing arena.
But the challenger had his moments, delivering effective single shots in a match where the techniques never quite clicked, with excessive holding spoiling the action.
The officials had it 96-94 for to the winner, with the third a even score.
"It wasn't my best showing but what do champions do? They win," the victor said in the ringside as he was faced boos from the spectators.
The British fighter bounced back after his first professional defeat - an thrilling contest with his previous opponent in last winter - to earn a 20th pro success.
Various analysts thought the challenger, 31, merited the decision but the contender suffered the second loss of his 28-match professional journey.
The Champion Claims Triumph in Slow Affair
The fighter's advancement has slowed in the past few years through management issues and considerable time of inactivity.
Previously predicted as the future of British boxing, he now stands trying to achieve expectations - possibly in what feels like a ultimate opportunity - under new promotional backing.
He opened tentatively, with the two boxers willing to take risks in a tentative early stages.
The challenger, whose sole prior loss came at super-middleweight against his former opponent in 2022 after breaking his hand during the bout, was competing in only his second bout at the higher weight class.
By the middle rounds, Parker had kept it close, making life awkward for the favorite, who worked behind a protective stance to edge the more effective periods.
The audience's tolerance diminished during frequent holding, with Parker going down several times during clinches.
The underdog finished the stronger, but many rounds were difficult to score. Nevertheless, former world champion Carl Frampton - providing analysis for the broadcast network - had it significantly in favor for the challenger, scoring for Buatsi just only one stanza.
The victor progresses, but with the presence of hard hitter David Benavidez, and Russian star Dmitry Bivol leading the category, the path to championship success - on this evidence - still seems difficult.
Ricky Hatton Memorial Inspires All-Manchester Battle
In the supporting bout, Arthur overcame Rea by divided decision in a terrific local rivalry fight to win the continental belt.
The stadium grew hushed for a profoundly moving tribute before the fight as ten bells rang in honor of local hero Hatton, who passed away at age 46 in last month.
It was the premier televised fight night in the location since Hatton's passing. As the concluding sound disappeared, the silence gave way to a chant of "there's just one Hatton".
The competition within the ring matched the feeling. The eventual winner was sent to the canvas by a significant blow flush on the jaw in the early round, getting up unsteadily to his feet on the referee's count.
But the Manchester United-red shorts of the fighter soon came forward again. From the other corner, the opponent - in rival City blue - was marked up early, noticeable damage appearing under his orbital area as the fighters traded powerful shots.
The challenger, twenty-seven, delivered effective strikes but the champion, 34, responded in kind with powerful upward punches as the pace seldom decreased over 12 rounds.
The victor narrowly won the decision with scoring tallies of even score, 115-113 and clearer margin, but both fighters were determined and brave, exactly what their inspiration the legend represented.
