UK light-heavyweight Buatsi made a winning yet disappointing debut to life under fresh promotional backing with a unanimous decision over Zach Parker in Manchester.
The Olympic medal winner's work rate appeared to earn him a split decision in a tight 10-round bout at the Manchester venue.
But the challenger had his moments, landing some telling clean blows in a contest where the approaches failed to mesh, with excessive holding marring the fight.
The officials judged it 96-94 for to the winner, with the third a 95-95 draw.
"It wasn't my finest showing but what do champions do? They succeed," the victor commented in the ring as he was met by disapproval from the crowd.
The Londoner returned to winning ways after his initial pro loss - an thrilling contest with his previous opponent in last winter - to claim a 20th pro success.
Various analysts thought Parker, 31, should have been awarded the victory but the Derbyshire fighter suffered the second loss of his 28-bout career.
The Champion Earns Victory in Slow Encounter
Buatsi's progress has slowed in recent times through management issues and long spells of inactivity.
Once tipped as the next star of UK boxing, he now stands trying to achieve expectations - possibly in what seems like a last chance - under fresh management.
He started carefully, with the two boxers willing to take risks in a cagey initial rounds.
The challenger, whose sole prior loss came at super-middleweight against John Ryder in 2022 after damaging his hand mid-fight, was participating in his second fight at light-heavyweight.
By the halfway stage, Parker had kept it close, making life awkward for Buatsi, who operated with a solid defense to barely take the better periods.
The crowd's patience decreased because of frequent holding, with Parker slipping to the canvas multiple occasions during clinches.
Parker ended stronger, but several stanzas were challenging to assess. Although, former world champion the boxing analyst - providing analysis for Dazn - had it significantly in favor for the challenger, awarding Buatsi just only one stanza.
The victor progresses, but with the presence of power puncher David Benavidez, and Eastern European fighter Dmitry Bivol leading the category, the path to championship success - on this evidence - still seems difficult.
Hatton Memorial Fuels Local Rivalry Battle
In the supporting bout, Arthur overcame Bradley Rea by split-decision in a terrific Manchester vs Manchester contest to win the European light heavyweight championship.
The venue became quiet for a profoundly moving memorial ahead of the contest as a bell ceremony tolled in honor of the city's native Hatton, who succumbed aged 46 in last month.
It was the premier televised boxing event in the urban center since Hatton's death. As the final chime faded, the stillness gave way to a shout of "there's just one Hatton".
The action during the bout matched the emotion. Arthur was knocked down by a powerful punch flush on the jaw in the early round, standing uncertainly to his feet on the eight count.
But the red-colored shorts of the fighter soon came forward again. Across the ring, Rea - in opposing blue - was injured soon, heavy swelling forming under his eye as the duo landed hard punches.
The challenger, twenty-seven, connected with strong blows but Arthur, 34, fought fire with fire with effective uppercuts as the action seldom decreased over the full distance.
Arthur edged the result with official scores of draw, 115-113 and wider gap, but each competitor were determined and brave, everything their hero Hatton stood for.
