UK light-heavyweight Buatsi made a winning yet unimpressive start to his career under recent management with a points victory over Zach Parker in Manchester.
The Olympic bronze medallist's activity level seemingly secured him a split decision in a close ten-round fight at the Manchester venue.
But Parker landed significant shots, landing some telling single shots in a match where the styles didn't complement each other, with excessive holding marring the action.
Two judges judged it 96-94 in favor to the winner, with the third a even score.
"It wasn't my finest performance but how do champions respond? They win," Buatsi stated in the ringside as he was met by negative reactions from the crowd.
The Londoner got back to winning after his maiden career setback - an memorable fight with Callum Smith in last winter - to claim a 20th career victory.
Some ringside observers thought the challenger, 31, should have been awarded the win but the British boxer endured the second loss of his 28-fight professional journey.
The Champion Earns Win in Dull Affair
The fighter's advancement has stalled in recent years through management issues and considerable time of lack of fights.
Previously predicted as the rising talent of the British fight scene, he now is positioned trying to achieve expectations - perhaps in what feels like a last chance - under new promotional backing.
He opened tentatively, with neither fighter ready to take risks in a tentative opening few rounds.
Parker, whose sole prior loss came at super middleweight against John Ryder in 2022 after suffering a hand injury in the contest, was competing in only his second fight at the higher weight class.
By the middle rounds, Parker had stayed in contention, causing problems for Buatsi, who utilized a protective stance to edge the cleaner stanzas.
The spectators' acceptance wore thin during constant clinching, with Parker going down various instances during clinches.
Parker closed well, but many rounds were challenging to assess. Although, ex-champion Carl Frampton - working with Dazn - had it significantly in favor for Parker, awarding Buatsi just one round.
Buatsi advances, but with the presence of hard hitter David Benavidez, and Russian star Dmitry Bivol leading the category, the path to championship success - on this evidence - still seems difficult.
Ricky Hatton Memorial Fuels Manchester Derby Fight
In the supporting bout, Arthur defeated Rea by divided decision in a outstanding Manchester vs Manchester battle to win the European light-heavyweight title.
The stadium grew hushed for a profoundly moving tribute prior to the bout as 10 bells tolled in memory of Manchester's own Ricky Hatton, who died aged 46 in last month.
It was the initial significant broadcast boxing event in the location since Hatton's death. As the final chime faded, the silence became a shout of "there's just one Ricky Hatton".
The competition within the ring matched the emotion. The eventual winner was sent to the canvas by a left hook squarely on the face in the initial stage, rising shakily to his footing on the eight count.
But the traditional red shorts of the fighter soon advanced again. From the other corner, Rea - in rival City blue - was injured early, significant bruising forming under his face as the pair traded punishing blows.
Rea, 27, landed power punches but Arthur, 34, fought fire with fire with stinging uppercuts as the intensity rarely dropped over twelve rounds.
The victor edged the decision with official scores of 114-114, narrow lead and wider gap, but both fighters were persistent and full of heart, everything their inspiration the legend represented.
