UK light heavyweight Buatsi earned a win yet unimpressive beginning to life under recent management with a unanimous decision over Zach Parker in Manchester.
The Olympic bronze medallist's work rate appeared to earn him a majority decision in a competitive 10-round contest at the Co-op Live Arena.
But Parker landed significant shots, connecting with powerful single shots in a match where the approaches failed to mesh, with frequent clinching disrupting the fight.
Two judges judged it 96-94 for to the winner, with the third a even score.
"It wasn't my greatest showing but what defines champions? They prevail," Buatsi commented in the ring as he was faced negative reactions from the spectators.
The Londoner returned to winning ways after his initial pro loss - an thrilling contest with his previous opponent in last winter - to secure a twentieth professional win.
Several boxing experts thought the challenger, 31, deserved the win but the contender endured the second defeat of his 28-bout career.
The Champion Claims Win in Slow Affair
The fighter's advancement has stalled in recent times through promotional disputes and considerable time of lack of fights.
Earlier forecast as the rising talent of the British fight scene, he now is positioned trying to fulfil that early promise - possibly in what appears to be a last chance - under fresh management.
He began cautiously, with neither fighter prepared to be aggressive in a cagey initial rounds.
Parker, whose sole prior loss came at super middleweight against his former opponent in 2022 after damaging his hand in the contest, was participating in his second bout at light-heavyweight.
By the middle rounds, Parker had stayed in contention, making life awkward for the favorite, who utilized a tight guard to narrowly win the more effective rounds.
The spectators' acceptance diminished amid constant clinching, with Parker falling to the floor several times during clinches.
Parker finished the stronger, but multiple periods were challenging to assess. Nevertheless, former world champion Carl Frampton - providing analysis for Dazn - had it strongly leaning for the challenger, scoring for Buatsi just only one stanza.
The victor advances, but with the likes of hard hitter David Benavidez, and Russian star Bivol dominating the weight class, the path to championship success - on this evidence - still looks steep.
Ricky Hatton Memorial Motivates Manchester Derby Battle
In the co-main event, Arthur beat Rea by close verdict in a outstanding local rivalry battle to capture the continental belt.
The stadium fell silent for a extremely emotional homage before the fight as a bell ceremony rang in honor of the city's native Ricky Hatton, who died aged 46 in recently.
It was the premier televised match card in the city since the passing of Hatton. As the concluding sound faded, the stillness became a roar of "only one Hatton".
The fighting inside the ropes reflected the sentiment. The eventual winner was knocked down by a left hook flush on the chin in the initial stage, rising shakily to his position on the eight count.
But the red-colored equipment of the fighter soon advanced again. From the other corner, Rea - in competitive blue - was injured soon, noticeable damage developing under his eye as the duo exchanged powerful shots.
Rea, twenty-seven, landed power punches but the champion, thirty-four, matched the intensity with effective uppercuts as the pace rarely dropped over 12 rounds.
Arthur edged the verdict with official scores of draw, narrow lead and clearer margin, but both fighters were persistent and full of heart, exactly what their hero Hatton embodied.
