British light heavyweight Buatsi secured a victory yet unimpressive start to his career under fresh promotional backing with a unanimous decision over Zach Parker in Manchester.
The Olympic bronze medallist's punch output likely gained him a judges' verdict in a tight 10-round fight at the Manchester venue.
But Parker had his moments, landing some telling single shots in a contest where the styles didn't complement each other, with constant grabbing marring the action.
Two judges judged it 96-94 for to the winner, with the third a 95-95.
"It wasn't my finest showing but what defines champions? They succeed," Buatsi said in the arena as he was met by disapproval from the spectators.
The Londoner bounced back after his maiden career setback - an epic battle with his previous opponent in last winter - to secure a 20th pro success.
Several boxing experts thought the challenger, 31, deserved the victory but the Derbyshire fighter suffered the second loss of his 28-bout professional journey.
Buatsi Secures Win in Uneventful Encounter
The fighter's advancement has stalled in recent times through promotional disputes and considerable time of inactivity.
Earlier forecast as the rising talent of UK boxing, he now stands trying to fulfil that early promise - perhaps in what appears to be a last chance - under fresh management.
He started carefully, with neither fighter prepared to take risks in a tentative opening few rounds.
The challenger, whose sole prior loss came at the lower weight class against John Ryder in two years ago after damaging his hand in the contest, was making just his second appearance at the higher weight class.
By the halfway stage, Parker had made it competitive, creating difficulties for the favorite, who utilized a tight guard to barely take the cleaner stanzas.
The spectators' acceptance decreased amid frequent holding, with Parker slipping to the canvas several times during grappling.
Parker closed well, but multiple periods were hard to judge. Nevertheless, ex-champion the boxing analyst - commentating on Dazn - had it strongly leaning for Parker, scoring for Buatsi just a single round.
Buatsi progresses, but with the presence of hard hitter David Benavidez, and Eastern European fighter Bivol ruling the division, the journey to titles - based on this performance - still looks steep.
Ricky Hatton Memorial Fuels Manchester Derby Battle
In the secondary fight, Lyndon Arthur beat Bradley Rea by divided decision in a outstanding local rivalry contest to win the European light-heavyweight championship.
The venue fell silent for a profoundly moving tribute before the fight as ten bells tolled in memory of Manchester's own Ricky Hatton, who succumbed aged 46 in September.
It was the first major televised fight night in the urban center since Hatton's death. As the final chime ended, the silence became a shout of "only one Ricky Hatton".
The action within the ring reflected the feeling. Arthur was knocked down by a left hook flush on the chin in the second round, rising shakily to his footing on the eight count.
But the red-colored attire of the fighter soon advanced again. From the other corner, the opponent - in opposing blue - was injured early, noticeable damage forming under his face as the duo exchanged hard punches.
The challenger, twenty-seven, connected with strong blows but Arthur, 34, responded in kind with effective uppercuts as the action seldom decreased over the full distance.
The victor narrowly won the result with scoring tallies of even score, narrow lead and 115-112, but both fighters were relentless and full of heart, everything their idol the legend stood for.
