UK light heavyweight Buatsi earned a win yet disappointing start to his career under new promoters with a points victory over Zach Parker in the Manchester arena.
The Olympic medal winner's activity level likely gained him a judges' verdict in a competitive 10-round bout at the boxing arena.
But Parker had his moments, connecting with powerful clean blows in a contest where the approaches failed to mesh, with frequent clinching marring the contest.
The officials had it 96-94 to the winner, with the third a 95-95.
"It wasn't my greatest display but what do champions do? They win," Buatsi stated in the ring as he was faced negative reactions from the spectators.
The British fighter returned to winning ways after his initial pro loss - an thrilling contest with Callum Smith in February - to earn a 20th pro success.
Some ringside observers felt Parker, thirty-one, merited the win but the British boxer experienced the second defeat of his 28-fight career.
Buatsi Earns Victory in Dull Encounter
His career development has stalled in the past few years through contract problems and considerable time of inactivity.
Previously predicted as the future of UK boxing, he now finds himself trying to achieve expectations - perhaps in what feels like a last chance - under new promotional backing.
He opened tentatively, with neither fighter willing to be aggressive in a calculated early stages.
Parker, whose only previous defeat came at super-middleweight against his former opponent in two years ago after damaging his hand mid-fight, was competing in only his second appearance at light heavyweight.
By the halfway stage, Parker had made it competitive, causing problems for Buatsi, who utilized a protective stance to barely take the better rounds.
The spectators' acceptance decreased amid frequent holding, with the challenger falling to the floor various instances during grappling.
The underdog finished the stronger, but multiple periods were challenging to assess. Although, former world champion the boxing analyst - providing analysis for Dazn - had it significantly in favor for the challenger, giving Buatsi just one round.
Buatsi advances, but with the likes of hard hitter Benavidez, and Eastern European fighter Dmitry Bivol dominating the weight class, the path to championship success - on this evidence - still seems difficult.
Ricky Hatton Homage Motivates All-Manchester Fight
In the supporting bout, Lyndon Arthur beat Bradley Rea by close verdict in a excellent local rivalry contest to win the continental belt.
The venue grew hushed for a deeply poignant memorial prior to the bout as a bell ceremony tolled in honor of the city's native Hatton, who died aged 46 in last month.
It was the initial significant broadcast match card in the location since Hatton's passing. As the concluding sound ended, the stillness became a chant of "only one Ricky Hatton".
The action during the bout equaled the feeling. Arthur was knocked down by a significant blow directly to the jaw in the second round, getting up unsteadily to his position on the count of eight.
But the Manchester United-red shorts of the fighter soon advanced again. On the opposite side, Rea - in opposing blue - was damaged early, noticeable damage developing under his orbital area as the duo landed powerful shots.
The challenger, twenty-seven, landed power punches but the champion, thirty-four, responded in kind with effective uppercuts as the pace rarely dropped over 12 rounds.
The victor edged the decision with official scores of 114-114, close margin and clearer margin, but both fighters were relentless and brave, all the qualities their hero Hatton stood for.
