UK light-heavyweight Buatsi secured a victory yet unimpressive beginning to life under fresh promotional backing with a points victory over Zach Parker in the Manchester arena.
The Olympic bronze medallist's work rate likely gained him a split decision in a tight 10-round contest at the Co-op Live Arena.
But Parker had his moments, landing some telling single shots in a contest where the approaches never quite clicked, with constant grabbing marring the fight.
The officials scored it 96-94 in favor to Buatsi, with the final judge a 95-95 draw.
"It wasn't my finest performance but how do champions respond? They prevail," the victor said in the arena as he was met by disapproval from the crowd.
The British fighter got back to winning after his maiden career setback - an memorable fight with Callum Smith in February - to secure a 20th career victory.
Some ringside observers felt the challenger, thirty-one, deserved the victory but the British boxer endured the second setback of his 28-bout career.
Buatsi Claims Triumph in Slow Match
The fighter's advancement has stalled in recent years through promotional disputes and extended periods of inactivity.
Earlier forecast as the next star of UK boxing, he now finds himself trying to realize his potential - maybe in what seems like a final roll of the dice - under new promotional backing.
He started carefully, with both competitors ready to overcommit in a calculated opening few rounds.
The challenger, whose only previous defeat came at super middleweight against his former opponent in 2022 after suffering a hand injury mid-fight, was participating in his second bout at the higher weight class.
By the halfway stage, Parker had kept it close, creating difficulties for Buatsi, who worked behind a protective stance to narrowly win the more effective periods.
The audience's tolerance decreased because of constant clinching, with the challenger slipping to the canvas various instances during close exchanges.
Parker closed well, but several stanzas were challenging to assess. However, ex-champion Carl Frampton - commentating on the broadcast network - had it strongly leaning for the challenger, giving Buatsi just a single round.
Buatsi moves on, but with the likes of hard hitter David Benavidez, and Eastern European fighter Bivol dominating the weight class, the path to championship success - based on this performance - still seems difficult.
Ricky Hatton Homage Fuels Manchester Derby Fight
In the co-main event, Arthur defeated Bradley Rea by close verdict in a excellent all-Manchester battle to secure the continental title.
The venue grew hushed for a profoundly moving tribute before the fight as ten bells rang in memory of Manchester's own Hatton, who died 46 years old in last month.
It was the premier televised fight night in the location since Hatton's death. As the last bell faded, the quiet gave way to a shout of "there's only one Hatton".
The action within the ring equaled the emotion. The eventual winner was knocked down by a left hook flush on the chin in the initial stage, rising shakily to his footing on the count of eight.
But the red-colored attire of the fighter soon came forward again. From the other corner, the opponent - in opposing blue - was injured early, significant bruising appearing under his face as the duo exchanged powerful shots.
The challenger, 27, landed power punches but the champion, 34, responded in kind with stinging uppercuts as the pace seldom decreased over twelve rounds.
Arthur barely secured the decision with judges scorecards of draw, 115-113 and 115-112, but the two athletes were determined and courageous, exactly what their hero Hatton embodied.
