British light-heavyweight Buatsi secured a victory yet unimpressive debut to his career under fresh promotional backing with a unanimous decision over Zach Parker in the Manchester arena.
The Olympic medal winner's activity level appeared to earn him a judges' verdict in a competitive 10-round contest at the Manchester venue.
But Parker found success, connecting with powerful single shots in a match where the styles never quite clicked, with frequent clinching disrupting the action.
The scoring judges had it 96-94 for to Buatsi, with the final judge a 95-95.
"It wasn't my greatest performance but what defines champions? They succeed," Buatsi commented in the arena as he was met by disapproval from the crowd.
The British fighter bounced back after his initial pro loss - an memorable fight with Callum Smith in last winter - to claim a twentieth professional win.
Various analysts thought Parker, thirty-one, should have been awarded the win but the contender suffered the second loss of his 28-fight professional journey.
Buatsi Earns Victory in Uneventful Encounter
Buatsi's progress has stalled in recent years through contract problems and extended periods of lack of fights.
Earlier forecast as the next star of British boxing, he now stands trying to achieve expectations - perhaps in what seems like a ultimate opportunity - under new promotional backing.
He began cautiously, with both competitors willing to be aggressive in a tentative early stages.
The challenger, whose sole prior loss came at super middleweight against John Ryder in 2022 after damaging his hand during the bout, was participating in his second appearance at light-heavyweight.
By the halfway stage, Parker had kept it close, causing problems for the favorite, who operated with a protective stance to barely take the cleaner rounds.
The audience's tolerance decreased during constant clinching, with Parker falling to the floor several times during grappling.
The underdog finished the stronger, but many rounds were hard to judge. However, ex-champion Carl Frampton - commentating on Dazn - had it strongly leaning for the challenger, scoring for Buatsi just a single round.
Buatsi moves on, but with the presence of hard hitter David Benavidez, and Russian champion Bivol ruling the division, the road to world glory - based on this performance - still seems difficult.
Hatton Tribute Inspires Manchester Derby Fight
In the secondary fight, Lyndon Arthur overcame Rea by split-decision in a terrific all-Manchester contest to secure the European light heavyweight title.
The stadium became quiet for a deeply poignant homage ahead of the contest as 10 bells sounded in honor of local hero Ricky Hatton, who succumbed aged 46 in September.
It was the first major televised match card in the location since Hatton's death. As the final chime disappeared, the quiet gave way to a roar of "there's only one Hatton".
The action inside the ropes equaled the emotion. The eventual winner was knocked down by a significant blow directly to the chin in the initial stage, rising shakily to his feet on the eight count.
But the red-colored attire of the fighter soon came forward again. From the other corner, Rea - in opposing blue - was marked up quickly, significant bruising forming under his eye as the fighters exchanged punishing blows.
The challenger, 27, delivered effective strikes but the champion, 34, matched the intensity with effective uppercuts as the pace rarely dropped over 12 rounds.
Arthur narrowly won the result with scoring tallies of draw, close margin and wider gap, but each competitor were persistent and courageous, exactly what their hero Hatton stood for.
