British light-heavyweight Buatsi earned a win yet underwhelming debut to life under new promoters with a decision win over Zach Parker in the Manchester arena.
The Olympic medal winner's activity level seemingly secured him a split decision in a tight ten-round contest at the Manchester venue.
But Parker landed significant shots, delivering effective clean blows in a fight where the techniques failed to mesh, with excessive holding disrupting the action.
The scoring judges judged it 96-94 for to the winner, with the third a even score.
"It wasn't my best performance but what do champions do? They win," Buatsi said in the ringside as he was faced negative reactions from the spectators.
The British fighter bounced back after his maiden career setback - an epic battle with Callum Smith in last winter - to secure a twentieth professional win.
Some ringside observers believed Parker, 31, deserved the decision but the British boxer suffered the second defeat of his 28-bout professional journey.
Buatsi Earns Victory in Slow Encounter
The fighter's advancement has slowed in the past few years through management issues and extended periods of lack of fights.
Once tipped as the next star of UK boxing, he now stands trying to achieve expectations - perhaps in what seems like a last chance - under recent support.
He opened tentatively, with the two boxers prepared to take risks in a cagey early stages.
Parker, whose single earlier setback came at the lower weight class against John Ryder in 2022 after damaging his hand during the bout, was competing in only his second appearance at light-heavyweight.
By the halfway stage, Parker had kept it close, creating difficulties for Buatsi, who operated with a solid defense to edge the better periods.
The spectators' acceptance decreased during regular grabbing, with the challenger falling to the floor several times during close exchanges.
The underdog finished the stronger, but multiple periods were difficult to score. Although, former world champion the boxing analyst - working with Dazn - had it strongly leaning for Parker, giving Buatsi just one round.
Buatsi moves on, but with the presence of hard hitter Benavidez, and Russian star Dmitry Bivol ruling the division, the journey to titles - on this evidence - still seems difficult.
Hatton Memorial Motivates Manchester Derby Battle
In the supporting bout, Lyndon Arthur overcame Rea by close verdict in a terrific Manchester vs Manchester battle to secure the European light heavyweight belt.
The venue became quiet for a extremely emotional memorial before the fight as ten bells tolled in memory of Manchester's own Ricky Hatton, who died aged 46 in recently.
It was the premier televised match card in the urban center since Hatton's passing. As the last bell disappeared, the stillness became a roar of "there's only one Ricky Hatton".
The competition inside the ropes matched the sentiment. Arthur was sent to the canvas by a powerful punch directly to the face in the early round, getting up unsteadily to his position on the eight count.
But the traditional red equipment of Arthur soon pressed ahead again. Across the ring, the opponent - in opposing blue - was marked up soon, noticeable damage forming under his face as the pair traded punishing blows.
The challenger, 27, delivered effective strikes but Arthur, 34, fought fire with fire with powerful upward punches as the intensity seldom decreased over twelve rounds.
The victor barely secured the verdict with judges scorecards of 114-114, 115-113 and wider gap, but both fighters were relentless and brave, all the qualities their hero the legend stood for.
