UK light-heavyweight Buatsi earned a win yet underwhelming beginning to life under fresh promotional backing 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 10-round bout at the boxing arena.
But Parker found success, landing some telling clean blows in a contest where the techniques never quite clicked, with constant grabbing marring the action.
The officials judged it 96-94 for to the winner, with the final judge a 95-95 draw.
"It wasn't my finest display but what do champions do? They succeed," the victor said in the ring as he was greeted with disapproval from the crowd.
The Londoner got back to winning after his first professional defeat - an memorable fight with his previous opponent in last winter - to claim a 20th pro success.
Some ringside observers believed Parker, thirty-one, deserved the win but the British boxer experienced the second setback of his 28-match career.
Buatsi Secures Triumph in Dull Encounter
The fighter's advancement has stalled in recent years through contract problems and long spells of lack of fights.
Previously predicted as the next star of British boxing, he now finds himself trying to fulfil that early promise - perhaps in what feels like a ultimate opportunity - under recent support.
He opened tentatively, with neither fighter willing to overcommit in a tentative opening few rounds.
The challenger, whose sole prior loss came at the lower weight class against John Ryder in two years ago after suffering a hand injury in the contest, was participating in his second appearance at the higher weight class.
By the fight's midpoint, the underdog had kept it close, making life awkward for Buatsi, who worked behind a tight guard to narrowly win the more effective rounds.
The crowd's patience wore thin amid frequent holding, with Parker slipping to the canvas various instances during close exchanges.
Parker closed well, but several stanzas were challenging to assess. Nevertheless, previous titleholder the boxing analyst - providing analysis for Dazn - had it particularly wide for Parker, scoring for Buatsi just one round.
The victor advances, but with the likes of power puncher David Benavidez, and Russian star Bivol ruling the division, the path to championship success - based on this performance - still looks steep.
Hatton Homage Fuels Manchester Derby Fight
In the co-main event, Arthur overcame Bradley Rea by divided decision in a terrific local rivalry contest to capture the European light heavyweight belt.
The arena became quiet for a deeply poignant homage ahead of the contest as ten bells tolled in remembrance of Manchester's own Ricky Hatton, who passed away 46 years old in last month.
It was the premier televised match card in the city since Hatton's death. As the last bell ended, the stillness gave way to a chant of "there's just one Hatton".
The fighting within the ring equaled the feeling. The eventual winner was floored by a significant blow flush on the chin in the second round, rising shakily to his position on the eight count.
But the Manchester United-red equipment of the fighter soon pressed ahead again. On the opposite side, Rea - in rival City blue - was injured early, significant bruising forming under his face as the duo traded powerful shots.
The challenger, 27, landed power punches but Arthur, thirty-four, fought fire with fire with stinging uppercuts as the intensity rarely dropped over twelve rounds.
Arthur barely secured the decision with scoring tallies of even score, close margin and wider gap, but each competitor were determined and full of heart, exactly what their idol the legend stood for.
