UK light heavyweight Buatsi made a winning yet underwhelming debut to life under new promoters with a points victory over Zach Parker in the Manchester arena.
The Olympic medal winner's work rate likely gained him a split decision in a tight 10-round fight at the boxing arena.
But Parker found success, connecting with powerful single shots in a fight where the techniques never quite clicked, with frequent clinching disrupting the contest.
Two judges had it 96-94 to Buatsi, with the final judge a 95-95 draw.
"It wasn't my best showing but what do champions do? They win," the victor said in the arena as he was met by boos from the audience.
The British fighter bounced back after his first professional defeat - an memorable fight with Callum Smith in February - to secure a 20th pro success.
Various analysts thought the challenger, thirty-one, merited the win but the Derbyshire fighter experienced the second loss of his 28-match professional journey.
The Champion Claims Triumph in Dull Encounter
Buatsi's progress has stalled in recent years through contract problems and extended periods of inactivity.
Once tipped as the future of the British fight scene, he now stands trying to fulfil that early promise - perhaps in what appears to be a last chance - under new promotional backing.
He opened tentatively, with neither fighter ready to take risks in a calculated initial rounds.
Parker, whose only previous defeat came at the lower weight class against his former opponent in 2022 after suffering a hand injury during the bout, was competing in only his second fight at the higher weight class.
By the halfway stage, the underdog had made it competitive, creating difficulties for the favorite, who operated with a solid defense to narrowly win the cleaner periods.
The crowd's patience decreased amid frequent holding, with the challenger falling to the floor several times during grappling.
The underdog closed well, but several stanzas were challenging to assess. Nevertheless, previous titleholder the boxing analyst - working with the broadcast network - had it particularly wide for Parker, scoring for Buatsi just one round.
The victor advances, but with the caliber of hard hitter David Benavidez, and Russian star Bivol leading the category, the journey to titles - judging by this showing - still looks steep.
Hatton Memorial Inspires Manchester Derby Fight
In the co-main event, Arthur defeated Rea by close verdict in a outstanding all-Manchester fight to win the continental belt.
The stadium fell silent for a extremely emotional memorial ahead of the contest as 10 bells sounded in honor of Manchester's own Hatton, who succumbed 46 years old in last month.
It was the first major televised boxing event in the location since Hatton's passing. As the concluding sound disappeared, the stillness became a chant of "there's just one Hatton".
The action inside the ropes matched the sentiment. Arthur was knocked down by a powerful punch directly to the face in the initial stage, standing uncertainly to his feet on the eight count.
But the traditional red attire of Arthur soon advanced again. From the other corner, the opponent - in opposing blue - was injured early, heavy swelling developing under his orbital area as the duo traded powerful shots.
The challenger, 27, delivered effective strikes but Arthur, thirty-four, responded in kind with powerful upward punches as the pace hardly diminished over twelve rounds.
The victor narrowly won the verdict with scoring tallies of 114-114, close margin and wider gap, but both fighters were persistent and courageous, everything their hero Hatton embodied.
