UK light heavyweight Buatsi earned a win yet disappointing debut to his career under fresh promotional backing with a unanimous decision over Zach Parker in Manchester.
The Olympic medal winner's work rate seemingly secured him a judges' verdict in a competitive ten-round fight at the Co-op Live Arena.
But Parker found success, landing some telling clean blows in a contest where the approaches never quite clicked, with frequent clinching disrupting the action.
The officials scored it 96-94 for to Buatsi, with the final judge a 95-95.
"It wasn't my finest showing but what defines champions? They prevail," Buatsi stated in the ringside as he was faced disapproval from the spectators.
The Londoner returned to winning ways after his first professional defeat - an memorable fight with his previous opponent in last winter - to earn a 20th career victory.
Various analysts believed the challenger, thirty-one, deserved the win but the British boxer experienced the second defeat of his 28-match career.
The Champion Secures Triumph in Slow Encounter
His career development has stalled in recent years through promotional disputes and long spells of inactivity.
Earlier forecast as the future of UK boxing, he now is positioned trying to realize his potential - possibly in what feels like a ultimate opportunity - under fresh management.
He opened tentatively, with both competitors ready 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 during the bout, was competing in only his second fight at the higher weight class.
By the fight's midpoint, the underdog had made it competitive, causing problems for the favorite, who worked behind a solid defense to edge the better periods.
The crowd's patience decreased because of frequent holding, with Parker going down several times during close exchanges.
Parker ended stronger, but multiple periods were hard to judge. Nevertheless, former world champion Carl Frampton - working with Dazn - had it particularly wide for Parker, awarding Buatsi just a single round.
The victor advances, but with the presence of hard hitter David Benavidez, and Russian star Bivol leading the category, the journey to titles - on this evidence - still seems difficult.
Ricky Hatton Tribute Fuels All-Manchester Battle
In the secondary fight, Arthur overcame Rea by divided decision in a outstanding all-Manchester battle to capture the continental title.
The arena fell silent for a profoundly moving tribute prior to the bout as a bell ceremony tolled in honor of local hero Ricky Hatton, who succumbed 46 years old in last month.
It was the premier televised match card in the city since the passing of Hatton. As the last bell ended, the stillness became a shout of "only one Ricky Hatton".
The fighting within the ring equaled the emotion. The eventual winner was knocked down by a significant blow directly to the chin in the initial stage, rising shakily to his footing on the eight count.
But the traditional red attire of Arthur soon pressed ahead again. On the opposite side, the opponent - in rival City blue - was damaged soon, noticeable damage developing under his face as the pair landed hard punches.
Rea, 27, connected with strong blows but the champion, thirty-four, responded in kind with powerful upward punches as the pace rarely dropped over the full distance.
Arthur narrowly won the verdict with official scores of even score, narrow lead and clearer margin, but each competitor were determined and full of heart, all the qualities their idol Hatton represented.
