UK light-heavyweight Buatsi made a winning yet underwhelming start to life under new promoters with a points victory over Zach Parker in Manchester.
The Olympic medal winner's activity level seemingly secured him a judges' verdict in a tight 10-round fight at the Manchester venue.
But the challenger had his moments, delivering effective clean blows in a fight where the styles never quite clicked, with constant grabbing marring the contest.
The officials scored it 96-94 to Buatsi, with the final judge a 95-95 draw.
"It wasn't my finest performance but how do champions respond? They win," Buatsi said in the ring as he was faced boos from the crowd.
The Londoner got back to winning after his initial pro loss - an memorable fight with his previous opponent in last winter - to claim a twentieth professional win.
Various analysts thought Parker, thirty-one, should have been awarded the victory but the British boxer experienced the second defeat of his 28-match professional journey.
Buatsi Secures Triumph in Slow Affair
The fighter's advancement has stalled in recent years through contract problems and considerable time of inactivity.
Once tipped as the next star of UK boxing, he now finds himself trying to realize his potential - maybe in what appears to be a ultimate opportunity - under new promotional backing.
He opened tentatively, with neither fighter ready to take risks in a cagey initial rounds.
The challenger, whose single earlier setback came at the lower weight class against his former opponent in 2022 after damaging his hand in the contest, was competing in only his second fight at light-heavyweight.
By the middle rounds, the underdog had stayed in contention, creating difficulties for the favorite, who worked behind a solid defense to edge the more effective rounds.
The spectators' acceptance wore thin amid constant clinching, with Parker going down multiple occasions during grappling.
Parker closed well, but many rounds were difficult to score. However, previous titleholder the boxing analyst - commentating on the broadcast network - had it particularly wide for Parker, scoring for Buatsi just a single round.
Buatsi moves on, but with the caliber of heavy hitter David Benavidez, and Russian star Bivol ruling the division, the road to world glory - on this evidence - still seems difficult.
Hatton Tribute Inspires All-Manchester Contest
In the supporting bout, Arthur defeated Bradley Rea by divided decision in a terrific all-Manchester contest to capture the continental title.
The arena fell silent for a extremely emotional homage before the fight as 10 bells sounded in remembrance of the city's native Hatton, who died at age 46 in recently.
It was the first major televised fight night in the location since Hatton's death. As the last bell faded, the silence gave way to a roar of "there's just one Ricky Hatton".
The fighting within the ring matched the feeling. The eventual winner was floored by a powerful punch flush on the jaw in the second round, standing uncertainly to his feet on the eight count.
But the red-colored equipment of Arthur soon advanced again. On the opposite side, the opponent - in opposing blue - was damaged soon, significant bruising developing under his eye as the pair traded hard punches.
The challenger, 27, landed power punches but Arthur, 34, responded in kind with stinging uppercuts as the intensity rarely dropped over 12 rounds.
The victor edged the verdict with scoring tallies of draw, close margin and 115-112, but both fighters were persistent and brave, everything their inspiration Hatton embodied.
