UK light heavyweight Buatsi secured a victory yet unimpressive beginning to his career under fresh promotional backing with a points victory over Zach Parker in the Manchester arena.
The Olympic medal winner's work rate seemingly secured him a majority decision in a tight 10-round fight at the boxing arena.
But Parker found success, landing some telling single shots in a contest where the techniques failed to mesh, with frequent clinching spoiling the action.
Two judges judged it 96-94 for to the winner, with the third a 95-95 draw.
"It wasn't my finest performance but what defines champions? They win," the victor said in the ringside as he was met by boos from the audience.
The British fighter bounced back after his initial pro loss - an thrilling contest with his previous opponent in February - to secure a 20th pro success.
Several boxing experts thought Parker, thirty-one, should have been awarded the decision but the British boxer experienced the second loss of his 28-fight professional journey.
Buatsi Secures Victory in Uneventful Match
The fighter's advancement has plateaued in the past few years through contract problems and considerable time of lack of fights.
Earlier forecast as the future of UK boxing, he now finds himself trying to achieve expectations - perhaps in what seems like a final roll of the dice - under fresh management.
He opened tentatively, with neither fighter willing to overcommit in a tentative opening few rounds.
The challenger, whose sole prior loss came at super-middleweight against John Ryder in 2022 after suffering a hand injury mid-fight, was participating in his second bout at the higher weight class.
By the halfway stage, Parker had kept it close, making life awkward for Buatsi, who operated with a solid defense to barely take the cleaner rounds.
The audience's tolerance decreased amid frequent holding, with the challenger going down various instances during close exchanges.
The underdog finished the stronger, but many rounds were hard to judge. Nevertheless, previous titleholder Carl Frampton - providing analysis for Dazn - had it strongly leaning for Parker, awarding Buatsi just a single round.
Buatsi moves on, but with the caliber of hard hitter Benavidez, and Russian champion Bivol ruling the division, the path to championship success - judging by this showing - still looks steep.
Ricky Hatton Tribute Inspires Manchester Derby Battle
In the supporting bout, Lyndon Arthur overcame Rea by split-decision in a excellent all-Manchester fight to capture the continental belt.
The stadium fell silent for a profoundly moving homage before the fight as a bell ceremony sounded in memory of local hero Hatton, who succumbed at age 46 in last month.
It was the initial significant broadcast match card in the urban center since Hatton's death. As the last bell faded, the quiet gave way to a shout of "there's just one Hatton".
The fighting within the ring equaled the feeling. Arthur was floored by a powerful punch squarely on the chin in the second round, rising shakily to his footing on the referee's count.
But the traditional red equipment of Arthur soon advanced again. On the opposite side, the opponent - in opposing blue - was injured early, heavy swelling forming under his face as the duo landed powerful shots.
The challenger, twenty-seven, connected with strong blows but Arthur, thirty-four, matched the intensity with effective uppercuts as the pace seldom decreased over twelve rounds.
The victor barely secured the result with official scores of even score, narrow lead and clearer margin, but the two athletes were determined and courageous, all the qualities their hero the legend embodied.
