UK light-heavyweight Buatsi made a winning yet underwhelming start to his career under new promoters with a decision win over Zach Parker in the Manchester arena.
The Olympic bronze medallist's activity level likely gained him a split decision in a tight ten-round contest at the Co-op Live Arena.
But Parker found success, connecting with powerful individual punches in a contest where the approaches failed to mesh, with excessive holding spoiling the fight.
The scoring judges had it 96-94 for to Buatsi, with the third a 95-95.
"It wasn't my best showing but how do champions respond? They win," Buatsi commented in the ring as he was faced boos from the audience.
The British fighter returned to winning ways after his maiden career setback - an thrilling contest with Callum Smith in February - to earn a 20th career victory.
Various analysts thought the challenger, 31, deserved the victory but the contender endured the second defeat of his 28-fight career.
The Champion Claims Triumph in Dull Affair
His career development has plateaued in recent years through promotional disputes and considerable time of inactivity.
Earlier forecast as the rising talent of the British fight scene, he now finds himself trying to fulfil that early promise - maybe in what feels like a ultimate opportunity - under recent support.
He started carefully, with both competitors ready to be aggressive in a calculated early stages.
The challenger, whose sole prior loss came at the lower weight class against John Ryder in 2022 after breaking his hand during the bout, was making just his second appearance at light heavyweight.
By the fight's midpoint, Parker had made it competitive, causing problems for Buatsi, who operated with a tight guard to narrowly win the more effective stanzas.
The crowd's patience decreased during frequent holding, with the challenger slipping to the canvas various instances during clinches.
The underdog finished the stronger, but many rounds were difficult to score. Although, ex-champion Carl Frampton - providing analysis for the broadcast network - had it strongly leaning for Parker, giving Buatsi just one round.
The victor progresses, but with the caliber of hard hitter Benavidez, and Russian champion Bivol leading the category, the road to world glory - on this evidence - still seems difficult.
Hatton Memorial Inspires Local Rivalry Fight
In the secondary fight, Arthur overcame Bradley Rea by divided decision in a terrific Manchester vs Manchester fight to win the continental belt.
The stadium fell silent for a profoundly moving homage prior to the bout as a bell ceremony rang in remembrance of Manchester's own Ricky Hatton, who passed away 46 years old in recently.
It was the premier televised fight night in the city since the passing of Hatton. As the last bell disappeared, the stillness became a roar of "only one Hatton".
The action inside the ropes reflected the sentiment. The eventual winner was knocked down by a left hook squarely on the jaw in the initial stage, getting up unsteadily to his footing on the count of eight.
But the red-colored shorts of the fighter soon came forward again. On the opposite side, the opponent - in opposing blue - was injured quickly, heavy swelling appearing under his face as the pair exchanged hard punches.
The challenger, twenty-seven, connected with strong blows but the champion, thirty-four, responded in kind with effective uppercuts as the intensity seldom decreased over the full distance.
Arthur edged the decision with official scores of 114-114, narrow lead and clearer margin, but both fighters were persistent and brave, exactly what their inspiration Hatton embodied.
