UK light heavyweight Buatsi earned a win yet unimpressive debut to his career under new promoters with a unanimous decision over Zach Parker in Manchester.
The Olympic bronze medallist's punch output likely gained him a judges' verdict in a competitive ten-round fight at the Manchester venue.
But Parker had his moments, connecting with powerful single shots in a fight where the styles didn't complement each other, with constant grabbing marring the contest.
Two judges had it 96-94 in favor to Buatsi, with the remaining official a 95-95.
"It wasn't my greatest showing but how do champions respond? They succeed," the victor said in the ringside as he was greeted with disapproval from the spectators.
The British fighter returned to winning ways after his initial pro loss - an epic battle with Callum Smith in February - to earn a twentieth professional win.
Some ringside observers thought Parker, 31, should have been awarded the victory but the Derbyshire fighter endured the second defeat of his 28-match professional journey.
The Champion Secures Triumph in Uneventful Affair
The fighter's advancement has plateaued in recent times through management issues and long spells of lack of fights.
Earlier forecast as the future of UK boxing, he now stands trying to achieve expectations - possibly in what feels like a last chance - under new promotional backing.
He opened tentatively, with neither fighter ready to take risks in a calculated 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 competing in only his second fight at light-heavyweight.
By the halfway stage, the underdog had kept it close, creating difficulties for the favorite, who worked behind a protective stance to barely take the better periods.
The spectators' acceptance wore thin amid constant clinching, with Parker falling to the floor multiple occasions during grappling.
Parker closed well, but several stanzas were challenging to assess. However, previous titleholder Carl Frampton - providing analysis for Dazn - had it significantly in favor for Parker, awarding Buatsi just only one stanza.
The victor progresses, but with the presence of power puncher David Benavidez, and Russian star Bivol dominating the weight class, the journey to titles - on this evidence - still appears challenging.
Hatton Tribute Fuels Local Rivalry Battle
In the supporting bout, Arthur overcame Bradley Rea by divided decision in a excellent all-Manchester fight to secure the continental belt.
The arena became quiet for a profoundly moving memorial ahead of the contest as ten bells tolled in memory of local hero Hatton, who succumbed 46 years old in last month.
It was the first major televised boxing event in the urban center since the passing of Hatton. As the last bell faded, the quiet gave way to a chant of "there's just one Ricky Hatton".
The action during the bout reflected the emotion. Arthur was floored by a powerful punch flush on the face in the second round, standing uncertainly to his feet on the eight count.
But the Manchester United-red attire of the fighter soon advanced again. On the opposite side, the opponent - in opposing blue - was marked up early, heavy swelling developing under his eye as the fighters landed hard punches.
Rea, twenty-seven, landed power punches but Arthur, thirty-four, responded in kind with powerful upward punches as the action seldom decreased over the full distance.
The victor narrowly won the verdict with judges scorecards of even score, 115-113 and 115-112, but both fighters were determined and brave, all the qualities their idol the legend represented.
