UK light heavyweight Buatsi secured a victory yet unimpressive 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 appeared to earn him a judges' verdict in a tight 10-round bout at the boxing arena.
But Parker had his moments, landing some telling single shots in a fight where the styles never quite clicked, with constant grabbing spoiling the contest.
The scoring judges judged it 96-94 to Buatsi, with the remaining official a 95-95.
"It wasn't my best performance but what do champions do? They succeed," the victor stated in the arena as he was faced disapproval from the audience.
The British fighter bounced back after his maiden career setback - an thrilling contest with his previous opponent in February - to earn a 20th career victory.
Various analysts believed the challenger, 31, deserved the win but the Derbyshire fighter experienced the second setback of his 28-bout professional journey.
The Champion Earns Victory in Slow Match
The fighter's advancement has plateaued in the past few years through contract problems and considerable time of lack of fights.
Previously predicted as the rising talent of British boxing, he now finds himself trying to realize his potential - perhaps in what feels like a last chance - under recent support.
He began cautiously, with neither fighter prepared to take risks in a tentative initial rounds.
Parker, whose single earlier setback came at super middleweight against John Ryder in 2022 after breaking his hand in the contest, was making just his second fight at light heavyweight.
By the middle rounds, Parker had stayed in contention, making life awkward for the favorite, who operated with a solid defense to edge the more effective stanzas.
The spectators' acceptance diminished during regular grabbing, with the challenger slipping to the canvas multiple occasions during grappling.
The underdog finished the stronger, but multiple periods were challenging to assess. Although, ex-champion Carl Frampton - providing analysis for Dazn - had it strongly leaning for Parker, scoring for Buatsi just only one stanza.
The victor progresses, but with the likes of heavy hitter Benavidez, and Russian champion Dmitry Bivol dominating the weight class, the road to world glory - on this evidence - still seems difficult.
Ricky Hatton Homage Fuels Manchester Derby Battle
In the co-main event, Arthur overcame Bradley Rea by close verdict in a terrific local rivalry contest to capture the continental belt.
The venue fell silent for a profoundly moving homage prior to the bout as a bell ceremony sounded in memory of local hero Hatton, who succumbed at age 46 in September.
It was the premier televised boxing event in the city since Hatton's death. As the concluding sound ended, the stillness became a roar of "there's just one Hatton".
The fighting during the bout equaled the sentiment. The eventual winner was knocked down by a significant blow flush on the chin in the second round, standing uncertainly to his position on the referee's count.
But the traditional red equipment of the fighter soon pressed ahead again. From the other corner, Rea - in competitive blue - was marked up quickly, heavy swelling forming under his face as the pair exchanged powerful shots.
Rea, 27, connected with strong blows but Arthur, thirty-four, responded in kind with effective uppercuts as the pace hardly diminished over the full distance.
The victor edged the result with judges scorecards of 114-114, 115-113 and clearer margin, but each competitor were determined and full of heart, everything their inspiration the legend stood for.
