UK light heavyweight Buatsi secured a victory yet unimpressive start to life under fresh promotional backing with a decision win 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 Co-op Live Arena.
But Parker found success, landing some telling single shots in a fight where the approaches failed to mesh, with frequent clinching marring the contest.
The scoring judges judged it 96-94 in favor to the winner, with the third a even score.
"It wasn't my finest display but how do champions respond? They prevail," the victor said in the ring as he was faced boos from the audience.
The Londoner bounced back after his first professional defeat - an thrilling contest with Callum Smith in February - to secure a 20th pro success.
Several boxing experts believed Parker, thirty-one, merited the decision but the contender endured the second setback of his 28-match professional journey.
The Champion Secures Win in Slow Encounter
The fighter's advancement has plateaued in recent times through contract problems and long spells of inactivity.
Earlier forecast as the rising talent of UK boxing, he now is positioned trying to achieve expectations - maybe in what feels like a final roll of the dice - under fresh management.
He opened tentatively, with both competitors prepared to overcommit in a cagey initial rounds.
The challenger, whose sole prior loss came at super-middleweight against John Ryder in two years ago after damaging his hand during the bout, was making just his second appearance at light heavyweight.
By the halfway stage, the underdog had made it competitive, making life awkward for Buatsi, who operated with a solid defense to edge the more effective stanzas.
The audience's tolerance decreased because of constant clinching, with Parker falling to the floor several times during clinches.
The underdog finished the stronger, but several stanzas were challenging to assess. Although, former world champion Carl Frampton - commentating on the broadcast network - had it particularly wide for Parker, awarding Buatsi just one round.
The victor moves on, but with the likes of hard hitter Benavidez, and Eastern European fighter Bivol leading the category, the journey to titles - based on this performance - still looks steep.
Ricky Hatton Tribute Fuels All-Manchester Contest
In the co-main event, Arthur overcame Bradley Rea by split-decision in a terrific Manchester vs Manchester battle to capture the European light-heavyweight championship.
The venue fell silent for a deeply poignant homage before the fight as ten bells rang in honor of Manchester's own Hatton, who died aged 46 in last month.
It was the premier televised match card in the urban center since the passing of Hatton. As the final chime ended, the silence gave way to a shout of "only one Hatton".
The action during the bout equaled the sentiment. Arthur was sent to the canvas by a significant blow directly to the face in the initial stage, standing uncertainly to his feet on the count of eight.
But the traditional red shorts of the fighter soon pressed ahead again. Across the ring, the opponent - in opposing blue - was injured quickly, heavy swelling developing under his orbital area as the pair exchanged punishing blows.
The challenger, twenty-seven, delivered effective strikes but Arthur, 34, responded in kind with stinging uppercuts as the pace hardly diminished over the full distance.
The victor barely secured the decision with scoring tallies of 114-114, close margin and clearer margin, but the two athletes were relentless and brave, everything their idol Hatton embodied.
