British light-heavyweight Buatsi secured a victory yet underwhelming debut to life under new promoters with a points victory over Zach Parker in Manchester.
The Olympic bronze medallist's work rate likely gained him a judges' verdict in a close ten-round contest at the Manchester venue.
But Parker landed significant shots, landing some telling single shots in a match where the styles never quite clicked, with excessive holding disrupting the action.
Two judges judged it 96-94 in favor to the winner, with the remaining official a 95-95.
"It wasn't my finest showing but how do champions respond? They prevail," the victor stated in the ringside as he was met by boos from the spectators.
The British fighter bounced back after his first professional defeat - an thrilling contest with Callum Smith in last winter - to earn a 20th career victory.
Various analysts felt Parker, 31, deserved the victory but the British boxer suffered the second loss of his 28-match career.
The Champion Secures Win in Uneventful Affair
The fighter's advancement has slowed in recent years through management issues and long spells of lack of fights.
Once tipped as the rising talent of UK boxing, he now stands trying to realize his potential - perhaps in what appears to be a ultimate opportunity - under fresh management.
He started carefully, with the two boxers prepared to be aggressive in a tentative initial rounds.
Parker, whose only previous defeat came at super middleweight against his former opponent in 2022 after suffering a hand injury mid-fight, was making just his second bout at light heavyweight.
By the fight's midpoint, the underdog had made it competitive, creating difficulties for Buatsi, who worked behind a tight guard to barely take the better periods.
The spectators' acceptance decreased during frequent holding, with Parker falling to the floor various instances during close exchanges.
Parker ended stronger, but multiple periods were challenging to assess. Nevertheless, former world champion Carl Frampton - providing analysis for Dazn - had it strongly leaning for the challenger, giving Buatsi just a single round.
Buatsi advances, but with the caliber of heavy hitter David Benavidez, and Eastern European fighter Dmitry Bivol leading the category, the road to world glory - judging by this showing - still seems difficult.
Ricky Hatton Tribute Fuels Local Rivalry Fight
In the supporting bout, Arthur overcame Rea by split-decision in a terrific Manchester vs Manchester fight to secure the European light-heavyweight title.
The arena fell silent for a extremely emotional homage prior to the bout as ten bells tolled in remembrance of the city's native Hatton, who succumbed aged 46 in last month.
It was the initial significant broadcast match card in the urban center since the passing of Hatton. As the concluding sound ended, the stillness gave way to a chant of "there's just one Ricky Hatton".
The fighting inside the ropes equaled the sentiment. Arthur was knocked down by a left hook flush on the face in the second round, standing uncertainly to his feet on the referee's count.
But the Manchester United-red shorts of Arthur soon came forward again. From the other corner, Rea - in rival City blue - was marked up quickly, significant bruising appearing under his eye as the duo exchanged hard punches.
The challenger, 27, delivered effective strikes but Arthur, 34, responded in kind with powerful upward punches as the action rarely dropped over the full distance.
The victor edged the result with official scores of 114-114, close margin and clearer margin, but both fighters were determined and courageous, everything their idol Hatton represented.
