UK light-heavyweight Buatsi earned a win yet disappointing beginning to his career under new promoters with a points victory over Zach Parker in the Manchester arena.
The Olympic bronze medallist's activity level appeared to earn him a majority decision in a tight ten-round bout at the boxing arena.
But Parker had his moments, landing some telling single shots in a contest where the styles never quite clicked, with constant grabbing spoiling the contest.
The scoring judges scored it 96-94 in favor to the winner, with the remaining official a even score.
"It wasn't my best performance but how do champions respond? They win," Buatsi commented in the ringside as he was greeted with negative reactions from the crowd.
The British fighter returned to winning ways after his maiden career setback - an thrilling contest with Callum Smith in February - to claim a twentieth professional win.
Several boxing experts felt Parker, thirty-one, should have been awarded the victory but the British boxer endured the second defeat of his 28-match professional journey.
Buatsi Secures Victory in Uneventful Encounter
His career development has plateaued in recent times through promotional disputes and considerable time of inactivity.
Earlier forecast as the next star of the British fight scene, he now stands trying to achieve expectations - maybe in what feels like a ultimate opportunity - under fresh management.
He opened tentatively, with neither fighter ready to overcommit in a tentative initial rounds.
The challenger, whose sole prior loss came at the lower weight class against John Ryder in two years ago after breaking his hand in the contest, was making just his second fight at light-heavyweight.
By the middle rounds, the underdog had kept it close, causing problems for Buatsi, who utilized a tight guard to edge the cleaner periods.
The audience's tolerance decreased amid frequent holding, with Parker going down various instances during grappling.
The underdog ended stronger, but multiple periods were hard to judge. Although, ex-champion the boxing analyst - working with Dazn - had it particularly wide for the challenger, giving Buatsi just a single round.
The victor moves on, but with the caliber of power puncher Benavidez, and Eastern European fighter Bivol dominating the weight class, the path to championship success - based on this performance - still appears challenging.
Ricky Hatton Homage Fuels All-Manchester Fight
In the supporting bout, Arthur overcame Rea by close verdict in a terrific Manchester vs Manchester battle to secure the European light-heavyweight belt.
The venue fell silent for a deeply poignant memorial before the fight as a bell ceremony rang in memory of the city's native Hatton, who succumbed aged 46 in last month.
It was the premier televised match card in the city since Hatton's passing. As the concluding sound disappeared, the quiet transitioned to a chant of "only one Ricky Hatton".
The action during the bout matched the feeling. Arthur was floored by a left hook directly to the face in the early round, rising shakily to his position on the eight count.
But the red-colored shorts of Arthur soon pressed ahead again. Across the ring, Rea - in opposing blue - was damaged soon, heavy swelling developing under his orbital area as the duo landed powerful shots.
The challenger, 27, landed power punches but Arthur, thirty-four, responded in kind with effective uppercuts as the intensity seldom decreased over 12 rounds.
Arthur edged the decision with official scores of draw, 115-113 and 115-112, but both fighters were determined and brave, exactly what their idol Hatton represented.
