UK light-heavyweight Buatsi secured a victory yet disappointing beginning to life under fresh promotional backing with a unanimous decision over Zach Parker in Manchester.
The Olympic medal winner's punch output seemingly secured him a judges' verdict in a close ten-round fight at the boxing arena.
But Parker found success, delivering effective individual punches in a fight where the styles never quite clicked, with constant grabbing disrupting the contest.
The scoring judges scored it 96-94 to Buatsi, with the final judge a 95-95.
"It wasn't my greatest display but what do champions do? They succeed," Buatsi stated in the arena as he was faced disapproval from the crowd.
The Londoner returned to winning ways after his maiden career setback - an epic battle with his previous opponent in February - to claim a 20th career victory.
Various analysts felt the challenger, 31, deserved the win but the contender experienced the second setback of his 28-fight professional journey.
Buatsi Secures Victory in Slow Match
Buatsi's progress has stalled in the past few years through management issues and long spells of inactivity.
Previously predicted as the next star of the British fight scene, he now is positioned trying to fulfil that early promise - maybe in what seems like a ultimate opportunity - under recent support.
He started carefully, with both competitors ready to take risks in a cagey early stages.
The challenger, whose only previous defeat came at super middleweight against his former opponent in 2022 after suffering a hand injury in the contest, was making just his second fight at light heavyweight.
By the fight's midpoint, Parker had made it competitive, causing problems for Buatsi, who worked behind a tight guard to edge the better stanzas.
The spectators' acceptance wore thin because of regular grabbing, with the challenger slipping to the canvas several times during grappling.
The underdog closed well, but many rounds were challenging to assess. Although, ex-champion the boxing analyst - commentating on Dazn - had it significantly in favor for Parker, scoring for Buatsi just only one stanza.
Buatsi progresses, but with the presence of power puncher David Benavidez, and Eastern European fighter Bivol dominating the weight class, the path to championship success - on this evidence - still looks steep.
Hatton Memorial Inspires All-Manchester Fight
In the supporting bout, Lyndon Arthur overcame Rea by close verdict in a terrific Manchester vs Manchester battle to secure the European light-heavyweight belt.
The arena grew hushed for a deeply poignant homage before the fight as 10 bells sounded in memory of local hero Hatton, who succumbed 46 years old in September.
It was the first major televised fight night in the urban center since the passing of Hatton. As the concluding sound disappeared, the quiet transitioned to a roar of "there's only one Ricky Hatton".
The action during the bout reflected the emotion. Arthur was knocked down by a left hook directly to the face in the initial stage, getting up unsteadily to his position on the count of eight.
But the Manchester United-red attire of the fighter soon advanced again. From the other corner, the opponent - in rival City blue - was injured soon, heavy swelling appearing under his eye as the fighters landed punishing blows.
Rea, 27, connected with strong blows but the champion, 34, matched the intensity with powerful upward punches as the intensity seldom decreased over the full distance.
The victor edged the verdict with official scores of even score, 115-113 and clearer margin, but each competitor were persistent and full of heart, all the qualities their idol Hatton stood for.
