UK light-heavyweight Buatsi made a winning yet disappointing start to his career under recent management with a points victory over Zach Parker in the Manchester arena.
The Olympic bronze medallist's activity level likely gained him a split decision in a tight 10-round contest at the boxing arena.
But the challenger found success, landing some telling individual punches in a fight where the styles failed to mesh, with excessive holding marring the contest.
The officials judged it 96-94 for to the winner, with the final judge a even score.
"It wasn't my finest performance but how do champions respond? They win," Buatsi commented in the ring as he was greeted with disapproval from the crowd.
The British fighter bounced back after his first professional defeat - an epic battle with Callum Smith in February - to secure a twentieth professional win.
Several boxing experts thought the challenger, 31, deserved the victory but the contender suffered the second defeat of his 28-bout career.
The Champion Secures Triumph in Dull Encounter
His career development has stalled in recent times through contract problems and long spells of lack of fights.
Previously predicted as the future of UK boxing, he now stands trying to realize his potential - possibly in what appears to be a last chance - under recent support.
He started carefully, with both competitors prepared to be aggressive in a cagey initial rounds.
Parker, whose only previous defeat came at super middleweight against his former opponent in two years ago after breaking his hand mid-fight, was participating in his second appearance at light heavyweight.
By the fight's midpoint, the underdog had stayed in contention, causing problems for Buatsi, who utilized a solid defense to narrowly win the better periods.
The audience's tolerance decreased because of constant clinching, with the challenger falling to the floor various instances during clinches.
The underdog closed well, but many rounds were hard to judge. Although, ex-champion the boxing analyst - commentating on Dazn - had it particularly wide for the challenger, giving Buatsi just only one stanza.
The victor moves on, but with the caliber of hard hitter David Benavidez, and Eastern European fighter Dmitry Bivol dominating the weight class, the journey to titles - judging by this showing - still appears challenging.
Ricky Hatton Homage Fuels Local Rivalry Fight
In the supporting bout, Arthur defeated Bradley Rea by close verdict in a outstanding Manchester vs Manchester battle to capture the continental championship.
The stadium became quiet for a deeply poignant homage before the fight as 10 bells sounded in remembrance of the city's native Hatton, who succumbed aged 46 in September.
It was the premier televised match card in the location since the passing of Hatton. As the final chime ended, the silence gave way to a shout of "only one Ricky Hatton".
The fighting during the bout reflected the emotion. Arthur was sent to the canvas by a significant blow squarely on the face in the initial stage, rising shakily to his footing on the count of eight.
But the red-colored equipment of Arthur soon advanced again. On the opposite side, Rea - in opposing blue - was injured soon, significant bruising forming under his orbital area as the fighters traded powerful shots.
Rea, twenty-seven, landed power punches but the champion, thirty-four, fought fire with fire with effective uppercuts as the intensity rarely dropped over 12 rounds.
Arthur narrowly won the decision with judges scorecards of 114-114, close margin and 115-112, but both fighters were persistent and full of heart, all the qualities their hero Hatton embodied.
