UK light-heavyweight Buatsi secured a victory yet underwhelming debut to life under new promoters with a unanimous decision over Zach Parker in the Manchester arena.
The Olympic bronze medallist's activity level likely gained him a judges' verdict in a tight 10-round fight at the Co-op Live Arena.
But Parker had his moments, delivering effective individual punches in a fight where the styles never quite clicked, with constant grabbing disrupting the contest.
The officials had it 96-94 in favor to the winner, with the remaining official a 95-95.
"It wasn't my best performance but how do champions respond? They win," the victor stated in the ring as he was faced disapproval from the spectators.
The Londoner got back to winning after his initial pro loss - an memorable fight with Callum Smith in February - to claim a 20th career victory.
Several boxing experts felt Parker, 31, should have been awarded the victory but the British boxer endured the second defeat of his 28-match career.
Buatsi Claims Win in Uneventful Encounter
Buatsi's progress has slowed in the past few years through promotional disputes and considerable time of inactivity.
Once tipped as the future of British boxing, he now is positioned trying to achieve expectations - maybe in what appears to be a last chance - under fresh management.
He began cautiously, with both competitors prepared to take risks in a calculated early stages.
Parker, whose single earlier setback came at the lower weight class against John Ryder in 2022 after breaking his hand in the contest, was participating in his second appearance at light heavyweight.
By the fight's midpoint, the underdog had made it competitive, making life awkward for Buatsi, who operated with a solid defense to edge the cleaner rounds.
The audience's tolerance wore thin during frequent holding, with the challenger falling to the floor various instances during clinches.
The underdog closed well, but multiple periods were difficult to score. However, former world champion Carl Frampton - working with Dazn - had it particularly wide for Parker, scoring for Buatsi just a single round.
The victor progresses, but with the likes of hard hitter David Benavidez, and Russian star Bivol leading the category, the path to championship success - judging by this showing - still looks steep.
Hatton Homage Inspires All-Manchester Battle
In the co-main event, Lyndon Arthur defeated Rea by close verdict in a outstanding Manchester vs Manchester fight to win the European light heavyweight title.
The arena became quiet for a profoundly moving tribute ahead of the contest as a bell ceremony tolled in memory of local hero Ricky Hatton, who succumbed 46 years old in last month.
It was the first major televised fight night in the location since Hatton's passing. As the final chime ended, the stillness became a roar of "there's only one Hatton".
The fighting inside the ropes equaled the emotion. The eventual winner was knocked down by a left hook squarely on the jaw in the initial stage, standing uncertainly to his footing on the count of eight.
But the traditional red shorts of the fighter soon advanced again. From the other corner, the opponent - in opposing blue - was marked up early, noticeable damage appearing under his face as the fighters landed punishing blows.
The challenger, twenty-seven, connected with strong blows but the champion, 34, fought fire with fire with stinging uppercuts as the action seldom decreased over 12 rounds.
Arthur edged the decision with official scores of draw, close margin and clearer margin, but both fighters were determined and courageous, everything their inspiration Hatton represented.
