UK light-heavyweight Buatsi secured a victory yet underwhelming start to life under fresh promotional backing with a unanimous decision over Zach Parker in the Manchester arena.
The Olympic bronze medallist's work rate appeared to earn him a split decision in a close 10-round bout at the Manchester venue.
But the challenger landed significant shots, connecting with powerful individual punches in a fight where the styles never quite clicked, with constant grabbing disrupting the action.
The officials scored it 96-94 for to the winner, with the remaining official a 95-95 draw.
"It wasn't my greatest display but what defines champions? They win," Buatsi said in the ringside as he was faced boos from the crowd.
The Londoner bounced back after his first professional defeat - an memorable fight with his previous opponent in last winter - to earn a twentieth professional win.
Several boxing experts felt Parker, thirty-one, merited the victory but the British boxer experienced the second loss of his 28-fight professional journey.
Buatsi Claims Triumph in Slow Encounter
His career development has plateaued in recent years through management issues and extended periods of inactivity.
Once tipped as the next star of UK boxing, he now stands trying to realize his potential - perhaps in what feels like a last chance - under recent support.
He started carefully, with neither fighter prepared to be aggressive in a cagey initial rounds.
Parker, whose only previous defeat came at super middleweight against John Ryder in 2022 after breaking his hand in the contest, was making just his second appearance at the higher weight class.
By the middle rounds, the underdog had made it competitive, creating difficulties for the favorite, who worked behind a solid defense to narrowly win the cleaner rounds.
The audience's tolerance wore thin amid frequent holding, with the challenger falling to the floor multiple occasions during close exchanges.
Parker ended stronger, but many rounds were difficult to score. However, ex-champion the boxing analyst - working with Dazn - had it strongly leaning for Parker, giving Buatsi just a single round.
The victor moves on, but with the caliber of heavy hitter Benavidez, and Russian champion Dmitry Bivol dominating the weight class, the road to world glory - judging by this showing - still seems difficult.
Hatton Homage Fuels All-Manchester Contest
In the supporting bout, Arthur defeated Bradley Rea by split-decision in a terrific Manchester vs Manchester fight to capture the European light heavyweight title.
The arena fell silent for a extremely emotional tribute prior to the bout as ten bells rang in remembrance of Manchester's own Ricky Hatton, who succumbed at age 46 in September.
It was the premier televised match card in the location since Hatton's death. As the concluding sound disappeared, the quiet became a shout of "there's just one Ricky Hatton".
The fighting within the ring equaled the emotion. Arthur was sent to the canvas by a powerful punch squarely on the jaw in the second round, standing uncertainly to his footing on the eight count.
But the red-colored attire of the fighter soon came forward again. From the other corner, Rea - in opposing blue - was marked up quickly, noticeable damage developing under his face as the pair landed powerful shots.
Rea, 27, connected with strong blows but Arthur, 34, fought fire with fire with stinging uppercuts as the action seldom decreased over 12 rounds.
Arthur edged the result with scoring tallies of even score, close margin and clearer margin, but the two athletes were persistent and courageous, everything their hero Hatton embodied.
