UK light heavyweight Buatsi secured a victory yet underwhelming debut to life under recent management with a decision win over Zach Parker in Manchester.
The Olympic bronze medallist's punch output likely gained him a majority decision in a tight ten-round contest at the boxing arena.
But the challenger had his moments, connecting with powerful single shots in a match where the styles never quite clicked, with excessive holding disrupting the action.
Two judges had it 96-94 for to the winner, with the third a even score.
"It wasn't my finest showing but how do champions respond? They prevail," the victor said in the ringside as he was greeted with disapproval from the crowd.
The British fighter got back to winning after his initial pro loss - an epic battle with Callum Smith in February - to secure a twentieth professional win.
Various analysts thought Parker, thirty-one, merited the win but the contender experienced the second loss of his 28-bout professional journey.
Buatsi Secures Triumph in Dull Match
His career development has plateaued in recent years through promotional disputes and extended periods of inactivity.
Previously predicted as the rising talent of the British fight scene, he now finds himself trying to fulfil that early promise - perhaps in what feels like a ultimate opportunity - under fresh management.
He started carefully, with both competitors prepared to overcommit in a cagey opening few rounds.
Parker, whose only previous defeat came at super middleweight against John Ryder in 2022 after damaging his hand during the bout, was participating in his second bout at light-heavyweight.
By the fight's midpoint, Parker had made it competitive, causing problems for the favorite, who worked behind a tight guard to edge the better periods.
The audience's tolerance decreased during constant clinching, with Parker falling to the floor several times during clinches.
Parker closed well, but several stanzas were difficult to score. Nevertheless, previous titleholder Carl Frampton - working with Dazn - had it significantly in favor for the challenger, awarding Buatsi just only one stanza.
Buatsi progresses, but with the presence of power puncher Benavidez, and Russian star Bivol leading the category, the journey to titles - on this evidence - still looks steep.
Hatton Tribute Motivates Manchester Derby Contest
In the supporting bout, Arthur beat Bradley Rea by close verdict in a excellent Manchester vs Manchester battle to win the European light-heavyweight title.
The stadium fell silent for a profoundly moving homage ahead of the contest as 10 bells sounded in honor of the city's native Ricky Hatton, who died aged 46 in last month.
It was the premier televised fight night in the location since Hatton's death. As the concluding sound ended, the quiet transitioned to a roar of "there's just one Ricky Hatton".
The fighting inside the ropes matched the sentiment. Arthur was sent to the canvas by a powerful punch squarely on the jaw in the second round, getting up unsteadily to his footing on the referee's count.
But the traditional red equipment of the fighter soon came forward again. Across the ring, the opponent - in rival City blue - was injured soon, noticeable damage developing under his face as the pair landed powerful shots.
The challenger, 27, connected with strong blows but Arthur, thirty-four, responded in kind with stinging uppercuts as the intensity hardly diminished over the full distance.
Arthur edged the decision with judges scorecards of draw, narrow lead and 115-112, but both fighters were persistent and courageous, exactly what their inspiration Hatton represented.
