UK light-heavyweight Buatsi earned a win yet disappointing beginning to his career under fresh promotional backing with a points victory over Zach Parker in Manchester.
The Olympic medal winner's activity level appeared to earn him a judges' verdict in a tight ten-round fight at the boxing arena.
But the challenger had his moments, delivering effective single shots in a contest where the styles never quite clicked, with frequent clinching disrupting the action.
The officials judged it 96-94 for to Buatsi, with the third a 95-95 draw.
"It wasn't my greatest performance but how do champions respond? They succeed," the victor said in the ring as he was faced disapproval from the spectators.
The Londoner got back to winning after his first professional defeat - an memorable fight with his previous opponent in last winter - to secure a 20th pro success.
Several boxing experts believed Parker, thirty-one, should have been awarded the win but the contender endured the second defeat of his 28-match professional journey.
Buatsi Secures Triumph in Slow Match
Buatsi's progress has slowed in recent times through contract problems and extended periods of lack of fights.
Earlier forecast as the future of UK boxing, he now stands trying to fulfil that early promise - possibly in what feels like a last chance - under recent support.
He opened tentatively, with the two boxers willing to take risks in a calculated opening few rounds.
Parker, whose single earlier setback came at the lower weight class against John Ryder in 2022 after breaking his hand mid-fight, was competing in only his second bout at light heavyweight.
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 periods.
The spectators' acceptance decreased during constant clinching, with the challenger falling to the floor multiple occasions during close exchanges.
The underdog finished the stronger, but many rounds were difficult to score. Nevertheless, former world champion the boxing analyst - providing analysis for the broadcast network - had it particularly wide for Parker, awarding Buatsi just one round.
The victor moves on, but with the likes of power puncher David Benavidez, and Eastern European fighter Dmitry Bivol ruling the division, the path to championship success - based on this performance - still seems difficult.
Ricky Hatton Homage Motivates Local Rivalry Fight
In the secondary fight, Lyndon Arthur defeated Rea by close verdict in a excellent local rivalry contest to secure the European light-heavyweight belt.
The venue became quiet for a deeply poignant tribute before the fight as 10 bells rang in remembrance of the city's native Hatton, who died aged 46 in September.
It was the first major televised fight night in the city since Hatton's passing. As the final chime disappeared, the silence transitioned to a shout of "there's just one Hatton".
The fighting during the bout equaled the sentiment. Arthur was floored by a left hook squarely on the jaw in the second round, rising shakily to his footing 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 early, heavy swelling developing under his orbital area as the duo traded punishing blows.
Rea, 27, delivered effective strikes but the champion, 34, fought fire with fire with powerful upward punches as the action hardly diminished over twelve rounds.
Arthur narrowly won the result with judges scorecards of 114-114, close margin and 115-112, but both fighters were determined and courageous, all the qualities their idol Hatton represented.
