British light heavyweight Buatsi secured a victory yet underwhelming start to life under fresh promotional backing with a unanimous decision over Zach Parker in Manchester.
The Olympic bronze medallist's work rate likely gained him a judges' verdict in a close 10-round fight at the Manchester venue.
But Parker found success, delivering effective individual punches in a match where the approaches failed to mesh, with frequent clinching marring the contest.
The officials judged it 96-94 to Buatsi, with the third a 95-95 draw.
"It wasn't my best display but how do champions respond? They win," the victor commented in the ring as he was met by disapproval from the audience.
The British fighter got back to winning after his maiden career setback - an memorable fight with Callum Smith in February - to claim a 20th pro success.
Some ringside observers thought the challenger, thirty-one, deserved the decision but the British boxer suffered the second loss of his 28-fight career.
Buatsi Claims Triumph in Slow Match
His career development has stalled in recent times through promotional disputes and considerable time of lack of fights.
Previously predicted as the rising talent of British boxing, he now is positioned trying to realize his potential - perhaps in what feels like a ultimate opportunity - under fresh management.
He started carefully, with the two boxers willing to take risks in a calculated opening few rounds.
The challenger, whose single earlier setback came at the lower weight class against John Ryder in 2022 after suffering a hand injury in the contest, was competing in only his second appearance at light heavyweight.
By the middle rounds, Parker had stayed in contention, making life awkward for Buatsi, who operated with a tight guard to barely take the more effective stanzas.
The spectators' acceptance wore thin amid regular grabbing, with the challenger falling to the floor several times during clinches.
Parker closed well, but several stanzas were hard to judge. Although, former world champion Carl Frampton - providing analysis for the broadcast network - had it strongly leaning for Parker, scoring for Buatsi just one round.
The victor moves on, but with the likes of heavy hitter David Benavidez, and Russian champion Dmitry Bivol dominating the weight class, the journey to titles - based on this performance - still appears challenging.
Ricky Hatton Memorial Inspires Local Rivalry Contest
In the supporting bout, Arthur overcame Bradley Rea by divided decision in a outstanding local rivalry contest to win the European light-heavyweight belt.
The venue grew hushed for a profoundly moving homage before the fight as 10 bells tolled in remembrance of local hero Hatton, who succumbed aged 46 in September.
It was the premier televised fight night in the location since Hatton's passing. As the concluding sound ended, the quiet became a chant of "only one Ricky Hatton".
The action inside the ropes reflected the emotion. The eventual winner was knocked down by a significant blow flush on the face in the initial stage, getting up unsteadily to his position on the referee's count.
But the traditional red attire of the fighter soon advanced again. Across the ring, Rea - in competitive blue - was marked up early, noticeable damage appearing under his orbital area as the pair exchanged powerful shots.
Rea, twenty-seven, connected with strong blows but the champion, thirty-four, fought fire with fire with powerful upward punches as the action seldom decreased over twelve rounds.
The victor barely secured the result with official scores of even score, 115-113 and wider gap, but each competitor were relentless and full of heart, all the qualities their inspiration the legend embodied.
