UK light heavyweight Buatsi secured a victory yet underwhelming beginning to life under new promoters with a points victory over Zach Parker in the Manchester arena.
The Olympic medal winner's punch output appeared to earn him a majority decision in a close ten-round fight at the Manchester venue.
But the challenger found success, connecting with powerful individual punches in a contest where the approaches failed to mesh, with excessive holding disrupting the contest.
The scoring judges scored it 96-94 in favor to Buatsi, with the remaining official a 95-95.
"It wasn't my greatest showing but how do champions respond? They succeed," Buatsi commented in the ring as he was faced disapproval from the audience.
The Londoner returned to winning ways after his maiden career setback - an memorable fight with Callum Smith in last winter - to claim a 20th career victory.
Several boxing experts felt Parker, 31, merited the victory but the contender experienced the second loss of his 28-bout professional journey.
The Champion Claims Triumph in Uneventful Match
Buatsi's progress has plateaued in the past few years through management issues and extended periods of inactivity.
Earlier forecast as the rising talent of the British fight scene, he now stands trying to realize his potential - maybe in what feels like a ultimate opportunity - under fresh management.
He opened tentatively, with the two boxers prepared to take risks in a tentative early stages.
The challenger, whose only previous defeat came at super-middleweight against his former opponent in 2022 after breaking his hand mid-fight, was competing in only his second fight at the higher weight class.
By the fight's midpoint, Parker had made it competitive, making life awkward for the favorite, who utilized a tight guard to barely take the cleaner stanzas.
The crowd's patience wore thin amid frequent holding, with the challenger falling to the floor several times during close exchanges.
The underdog ended stronger, but many rounds were hard to judge. Nevertheless, ex-champion Carl Frampton - commentating on Dazn - had it particularly wide for Parker, awarding Buatsi just only one stanza.
The victor moves on, but with the caliber of heavy hitter David Benavidez, and Eastern European fighter Bivol leading the category, the road to world glory - on this evidence - still looks steep.
Hatton Tribute Inspires All-Manchester Battle
In the supporting bout, Lyndon Arthur beat Rea by split-decision in a outstanding local rivalry battle to win the continental belt.
The venue fell silent for a profoundly moving memorial before the fight as 10 bells tolled in honor of Manchester's own Ricky Hatton, who passed away 46 years old in last month.
It was the first major televised match card in the city since the passing of Hatton. As the final chime faded, the quiet became a shout of "only one Ricky Hatton".
The fighting within the ring equaled the feeling. The eventual winner was knocked down by a significant blow squarely on the jaw in the initial stage, standing uncertainly to his position on the count of eight.
But the traditional red attire of Arthur soon came forward again. From the other corner, the opponent - in competitive blue - was marked up early, noticeable damage forming under his face as the fighters landed powerful shots.
Rea, twenty-seven, delivered effective strikes but Arthur, thirty-four, responded in kind with effective uppercuts as the intensity hardly diminished over the full distance.
Arthur barely secured the result with judges scorecards of draw, close margin and wider gap, but each competitor were relentless and courageous, exactly what their hero the legend stood for.
