British light-heavyweight Buatsi made a winning yet underwhelming debut to life under fresh promotional backing with a unanimous decision over Zach Parker in Manchester.
The Olympic medal winner's work rate likely gained him a split decision in a close ten-round bout at the boxing arena.
But Parker had his moments, connecting with powerful individual punches in a fight where the techniques didn't complement each other, with frequent clinching marring the contest.
Two judges scored it 96-94 for to the winner, with the final judge a 95-95.
"It wasn't my best showing but what defines champions? They win," the victor commented in the arena as he was greeted with disapproval from the crowd.
The British fighter bounced back after his initial pro loss - an epic battle with Callum Smith in last winter - to claim a 20th pro success.
Various analysts thought Parker, thirty-one, should have been awarded the victory but the contender suffered the second setback of his 28-match career.
The Champion Claims Victory in Slow Match
His career development has stalled in recent years through contract problems and long spells of lack of fights.
Previously predicted as the rising talent of UK boxing, he now finds himself trying to achieve expectations - perhaps in what seems like a last chance - under new promotional backing.
He started carefully, with both competitors ready to be aggressive in a calculated initial rounds.
Parker, whose only previous defeat came at the lower weight class against John Ryder in 2022 after suffering a hand injury mid-fight, was participating in his second bout at light heavyweight.
By the halfway stage, the underdog had stayed in contention, making life awkward for Buatsi, who utilized a solid defense to edge the better stanzas.
The audience's tolerance decreased amid regular grabbing, with Parker slipping to the canvas various instances during clinches.
The underdog finished the stronger, but several stanzas were hard to judge. Nevertheless, previous titleholder Carl Frampton - commentating on the broadcast network - had it particularly wide for the challenger, giving Buatsi just a single round.
Buatsi advances, but with the caliber of hard hitter David Benavidez, and Eastern European fighter Bivol ruling the division, the path to championship success - on this evidence - still looks steep.
Hatton Memorial Fuels Local Rivalry Contest
In the supporting bout, Arthur overcame Rea by close verdict in a excellent local rivalry battle to capture the continental title.
The stadium fell silent for a extremely emotional memorial prior to the bout as a bell ceremony tolled in memory of local hero Ricky Hatton, who passed away at age 46 in September.
It was the initial significant broadcast match card in the location since Hatton's passing. As the concluding sound ended, the silence became a chant of "there's just one Hatton".
The action during the bout reflected the feeling. The eventual winner was floored by a significant blow squarely on the chin in the early round, rising shakily to his footing on the eight count.
But the Manchester United-red equipment of the fighter soon pressed ahead again. Across the ring, the opponent - in rival City blue - was damaged soon, heavy swelling appearing under his eye as the duo exchanged hard punches.
The challenger, twenty-seven, landed power punches but the champion, 34, fought fire with fire with powerful upward punches as the intensity rarely dropped over twelve rounds.
The victor edged the decision with judges scorecards of 114-114, 115-113 and wider gap, but each competitor were persistent and brave, exactly what their hero the legend represented.
