British light-heavyweight Buatsi earned a win yet disappointing start to life under recent management with a points victory over Zach Parker in the Manchester arena.
The Olympic bronze medallist's work rate likely gained him a split decision in a close ten-round fight at the boxing arena.
But the challenger landed significant shots, connecting with powerful clean blows in a match where the techniques didn't complement each other, with excessive holding spoiling the fight.
The scoring judges had it 96-94 in favor to Buatsi, with the third a even score.
"It wasn't my greatest display but what defines champions? They win," the victor commented in the ringside as he was met by boos from the crowd.
The British fighter returned to winning ways after his first professional defeat - an epic battle with his previous opponent in February - to claim a twentieth professional win.
Various analysts thought Parker, thirty-one, deserved the victory but the Derbyshire fighter suffered the second setback of his 28-fight professional journey.
The Champion Claims Triumph in Uneventful Match
The fighter's advancement has slowed in recent years through promotional disputes and extended periods of lack of fights.
Once tipped as the future of British boxing, he now finds himself trying to achieve expectations - perhaps in what feels like a last chance - under fresh management.
He started carefully, with neither fighter prepared to overcommit in a tentative opening few rounds.
The challenger, whose only previous defeat came at super middleweight against his former opponent in two years ago after breaking his hand during the bout, was making just his second bout at the higher weight class.
By the middle rounds, Parker had stayed in contention, creating difficulties for Buatsi, who operated with a tight guard to edge the better periods.
The audience's tolerance diminished amid frequent holding, with the challenger slipping to the canvas various instances during clinches.
The underdog finished the stronger, but many rounds were hard to judge. Although, previous titleholder Carl Frampton - commentating on Dazn - had it strongly leaning for the challenger, awarding Buatsi just a single round.
Buatsi moves on, but with the presence of power puncher Benavidez, and Eastern European fighter Dmitry Bivol dominating the weight class, the path to championship success - judging by this showing - still looks steep.
Hatton Tribute Motivates All-Manchester Fight
In the co-main event, Arthur overcame Rea by close verdict in a terrific Manchester vs Manchester contest to capture the continental title.
The stadium grew hushed for a profoundly moving tribute before the fight as a bell ceremony sounded in memory of the city's native Hatton, who died aged 46 in September.
It was the premier televised match card in the location since Hatton's passing. As the final chime faded, the silence gave way to a roar of "only one Hatton".
The action during the bout reflected the feeling. The eventual winner was sent to the canvas by a left hook directly to the face in the early round, standing uncertainly to his position on the count of eight.
But the Manchester United-red attire of the fighter soon came forward again. From the other corner, the opponent - in rival City blue - was injured early, noticeable damage appearing under his orbital area as the pair exchanged punishing blows.
Rea, 27, delivered effective strikes but Arthur, thirty-four, fought fire with fire with powerful upward punches as the pace seldom decreased over 12 rounds.
The victor edged the verdict with official scores of even score, 115-113 and clearer margin, but the two athletes were relentless and full of heart, all the qualities their idol Hatton embodied.
