British light-heavyweight Buatsi made a winning yet underwhelming beginning to his career under fresh promotional backing with a decision win over Zach Parker in the Manchester arena.
The Olympic medal winner's work rate likely gained him a split decision in a close 10-round fight at the Manchester venue.
But Parker landed significant shots, delivering effective clean blows in a match where the techniques failed to mesh, with frequent clinching disrupting the action.
The scoring judges judged it 96-94 for to Buatsi, with the third a even score.
"It wasn't my best performance but how do champions respond? They succeed," Buatsi commented in the arena as he was met by negative reactions from the audience.
The British fighter bounced back after his first professional defeat - an epic battle with Callum Smith in February - to claim a 20th pro success.
Various analysts felt Parker, thirty-one, merited the win but the Derbyshire fighter endured the second loss of his 28-match professional journey.
The Champion Secures Victory in Slow Affair
His career development has stalled in recent times through management issues and considerable time of lack of fights.
Previously predicted as the future of UK boxing, he now stands trying to fulfil that early promise - possibly in what feels like a final roll of the dice - under fresh management.
He started carefully, with neither fighter ready to be aggressive in a calculated opening few rounds.
The challenger, whose only previous defeat came at the lower weight class against John Ryder in 2022 after suffering a hand injury during the bout, was competing in only his second bout at light-heavyweight.
By the fight's midpoint, Parker had made it competitive, creating difficulties for Buatsi, who operated with a tight guard to barely take the cleaner rounds.
The spectators' acceptance wore thin during frequent holding, with Parker going down several times during grappling.
The underdog ended stronger, but many rounds were difficult to score. Nevertheless, former world champion Carl Frampton - commentating on Dazn - had it strongly leaning for the challenger, giving Buatsi just a single round.
The victor advances, but with the presence of power puncher David Benavidez, and Eastern European fighter Bivol leading the category, the path to championship success - on this evidence - still appears challenging.
Ricky Hatton Tribute Motivates All-Manchester Battle
In the co-main event, Lyndon Arthur overcame Rea by divided decision in a terrific Manchester vs Manchester fight to secure the European light heavyweight belt.
The stadium became quiet for a extremely emotional homage ahead of the contest as 10 bells rang in memory of the city's native Ricky Hatton, who succumbed 46 years old in last month.
It was the initial significant broadcast match card in the city since Hatton's passing. As the final chime disappeared, the silence became a chant of "there's just one Ricky Hatton".
The competition inside the ropes reflected the feeling. The eventual winner was floored by a left hook flush on the jaw in the initial stage, standing uncertainly to his footing on the referee's count.
But the red-colored attire of the fighter soon pressed ahead again. On the opposite side, the opponent - in opposing blue - was marked up early, heavy swelling developing under his orbital area as the duo exchanged powerful shots.
Rea, 27, delivered effective strikes but the champion, 34, matched the intensity with powerful upward punches as the action hardly diminished over the full distance.
The victor barely secured the decision with official scores of 114-114, narrow lead and clearer margin, but the two athletes were relentless and full of heart, exactly what their idol Hatton stood for.
