British light heavyweight Buatsi secured a victory yet underwhelming debut to his career under new promoters with a unanimous decision over Zach Parker in the Manchester arena.
The Olympic bronze medallist's punch output seemingly secured him a split decision in a competitive ten-round fight at the Manchester venue.
But the challenger had his moments, landing some telling single shots in a fight where the approaches never quite clicked, with excessive holding marring the contest.
Two judges had it 96-94 in favor to the winner, with the remaining official a 95-95.
"It wasn't my finest showing but what defines champions? They prevail," the victor commented in the ring as he was faced negative reactions from the audience.
The British fighter got back to winning after his maiden career setback - an memorable fight with his previous opponent in February - to secure a 20th career victory.
Several boxing experts believed the challenger, 31, merited the victory but the Derbyshire fighter endured the second loss of his 28-bout professional journey.
The Champion Claims Victory in Uneventful Encounter
Buatsi's progress has slowed in recent times through management issues and considerable time of lack of fights.
Earlier forecast as the next star of the British fight scene, he now stands trying to achieve expectations - maybe in what seems like a ultimate opportunity - under new promotional backing.
He started carefully, with neither fighter willing to overcommit in a cagey initial rounds.
The challenger, whose single earlier setback came at the lower weight class against his former opponent in two years ago after damaging his hand mid-fight, was making just his second bout at the higher weight class.
By the fight's midpoint, Parker had stayed in contention, making life awkward for Buatsi, who worked behind a protective stance to narrowly win the cleaner periods.
The crowd's patience diminished during regular grabbing, with the challenger slipping to the canvas multiple occasions during close exchanges.
The underdog ended stronger, but multiple periods were challenging to assess. Although, ex-champion Carl Frampton - working with Dazn - had it significantly in favor for the challenger, giving Buatsi just one round.
The victor advances, but with the caliber of heavy hitter David Benavidez, and Russian champion Bivol leading the category, the road to world glory - judging by this showing - still seems difficult.
Hatton Memorial Inspires Manchester Derby Fight
In the co-main event, Lyndon Arthur overcame Bradley Rea by split-decision in a terrific Manchester vs Manchester battle to secure the continental championship.
The stadium fell silent for a deeply poignant homage ahead of the contest as a bell ceremony sounded in remembrance of the city's native Ricky Hatton, who succumbed aged 46 in September.
It was the premier televised match card in the location since Hatton's death. As the last bell faded, the stillness gave way to a chant of "there's just one Hatton".
The competition during the bout equaled the emotion. Arthur was knocked down by a powerful punch squarely on the face in the second round, getting up unsteadily to his feet on the referee's count.
But the traditional red equipment of the fighter soon advanced again. Across the ring, Rea - in opposing blue - was damaged soon, significant bruising appearing under his orbital area as the duo landed hard punches.
The challenger, twenty-seven, delivered effective strikes but the champion, 34, matched the intensity with powerful upward punches as the action seldom decreased over twelve rounds.
The victor narrowly won the decision with judges scorecards of draw, narrow lead and wider gap, but each competitor were determined and full of heart, everything their idol Hatton stood for.
