British light heavyweight Buatsi earned a win yet disappointing start to his career under fresh promotional backing with a points victory over Zach Parker in Manchester.
The Olympic medal winner's work rate likely gained him a judges' verdict in a close 10-round bout at the Co-op Live Arena.
But the challenger landed significant shots, landing some telling single shots in a contest where the approaches never quite clicked, with constant grabbing spoiling the fight.
Two judges had it 96-94 for to the winner, with the remaining official a even score.
"It wasn't my finest showing but what do champions do? They prevail," Buatsi commented in the ring as he was greeted with negative reactions from the crowd.
The Londoner returned to winning ways after his initial pro loss - an epic battle with Callum Smith in last winter - to earn a twentieth professional win.
Various analysts felt Parker, 31, should have been awarded the decision but the contender experienced the second defeat of his 28-fight professional journey.
Buatsi Earns Victory in Dull Affair
His career development has stalled in the past few years through promotional disputes and long spells of inactivity.
Previously predicted as the rising talent of UK boxing, he now stands trying to fulfil that early promise - possibly in what feels like a ultimate opportunity - under fresh management.
He began cautiously, with both competitors willing to take risks in a cagey early stages.
Parker, whose only previous defeat came at super-middleweight against John Ryder in 2022 after damaging his hand in the contest, was participating in his second bout at light heavyweight.
By the halfway stage, Parker had kept it close, causing problems for the favorite, who utilized a solid defense to edge the more effective periods.
The audience's tolerance decreased amid frequent holding, with the challenger slipping to the canvas various instances during close exchanges.
Parker ended stronger, but multiple periods were hard to judge. However, former world champion the boxing analyst - working with Dazn - had it strongly leaning for the challenger, awarding Buatsi just one round.
Buatsi progresses, but with the presence of heavy hitter Benavidez, and Russian star Dmitry Bivol ruling the division, the road to world glory - on this evidence - still seems difficult.
Ricky Hatton Tribute Motivates All-Manchester Battle
In the supporting bout, Arthur beat Rea by divided decision in a outstanding all-Manchester fight to capture the continental title.
The venue became quiet for a profoundly moving homage prior to the bout as ten bells rang in remembrance of Manchester's own Hatton, who died 46 years old in September.
It was the premier televised fight night in the city since the passing of Hatton. As the last bell disappeared, the silence became a shout of "there's only one Hatton".
The action during the bout reflected the emotion. The eventual winner was sent to the canvas by a significant blow directly to the face in the early round, getting up unsteadily to his footing on the referee's count.
But the Manchester United-red equipment of Arthur soon pressed ahead again. From the other corner, the opponent - in opposing blue - was marked up soon, noticeable damage appearing under his eye as the pair traded punishing blows.
The challenger, 27, connected with strong blows but the champion, 34, fought fire with fire with stinging uppercuts as the pace seldom decreased over the full distance.
Arthur barely secured the verdict with judges scorecards of even score, close margin and wider gap, but each competitor were determined and brave, all the qualities their idol Hatton embodied.
