UK light-heavyweight Buatsi earned a win yet unimpressive beginning to his career under fresh promotional backing with a decision win over Zach Parker in the Manchester arena.
The Olympic bronze medallist's activity level seemingly secured him a judges' verdict in a tight 10-round fight at the Co-op Live Arena.
But the challenger landed significant shots, delivering effective clean blows in a contest where the techniques didn't complement each other, with excessive holding marring the fight.
Two judges judged it 96-94 in favor to the winner, with the final judge a 95-95 draw.
"It wasn't my greatest showing but what defines champions? They win," Buatsi said in the ringside as he was faced boos from the spectators.
The Londoner bounced back after his initial pro loss - an memorable fight with his previous opponent in last winter - to claim a 20th pro success.
Various analysts believed Parker, thirty-one, merited the victory but the contender experienced the second defeat of his 28-bout professional journey.
Buatsi Earns Triumph in Slow Match
His career development has slowed in recent times through promotional disputes and long spells of inactivity.
Previously predicted as the rising talent of British boxing, he now is positioned trying to achieve expectations - possibly in what appears to be a last chance - under new promotional backing.
He opened tentatively, with neither fighter prepared to overcommit in a tentative initial rounds.
Parker, whose single earlier setback came at super-middleweight against his former opponent in 2022 after damaging his hand in the contest, was participating in his second appearance at light-heavyweight.
By the fight's midpoint, Parker had kept it close, making life awkward for Buatsi, who worked behind a tight guard to barely take the more effective periods.
The crowd's patience diminished amid regular grabbing, with Parker falling to the floor multiple occasions during close exchanges.
Parker ended stronger, but many rounds were challenging to assess. Nevertheless, ex-champion the boxing analyst - working with Dazn - had it particularly wide for the challenger, scoring for Buatsi just a single round.
Buatsi moves on, but with the likes of heavy hitter David Benavidez, and Russian champion Dmitry Bivol ruling the division, the journey to titles - on this evidence - still seems difficult.
Ricky Hatton Memorial Inspires Local Rivalry Battle
In the secondary fight, Lyndon Arthur overcame Bradley Rea by close verdict in a terrific local rivalry battle to win the European light heavyweight championship.
The stadium fell silent for a deeply poignant memorial before the fight as 10 bells sounded in memory of local hero Ricky Hatton, who succumbed aged 46 in September.
It was the initial significant broadcast fight night in the city since the passing of Hatton. As the last bell faded, the silence transitioned to a roar of "only one Ricky Hatton".
The competition within the ring matched the sentiment. The eventual winner was knocked down by a significant blow flush on the jaw in the second round, standing uncertainly to his position on the count of eight.
But the traditional red shorts of the fighter soon came forward again. Across the ring, Rea - in competitive blue - was damaged quickly, significant bruising forming under his orbital area as the pair exchanged hard punches.
The challenger, 27, landed power punches but Arthur, thirty-four, responded in kind with powerful upward punches as the action hardly diminished over the full distance.
Arthur narrowly won the verdict with scoring tallies of even score, narrow lead and clearer margin, but the two athletes were determined and courageous, all the qualities their idol the legend stood for.
