British light heavyweight Buatsi secured a victory yet unimpressive debut to his career under fresh promotional backing with a decision win over Zach Parker in Manchester.
The Olympic medal winner's activity level appeared to earn him a split decision in a competitive 10-round fight at the Manchester venue.
But Parker landed significant shots, landing some telling single shots in a contest where the styles didn't complement each other, with frequent clinching spoiling the contest.
The officials scored it 96-94 in favor to the winner, with the third a 95-95.
"It wasn't my finest display but what do champions do? They succeed," Buatsi said in the ring as he was greeted with boos from the spectators.
The Londoner bounced back after his first professional defeat - an memorable fight with Callum Smith in February - to secure a 20th career victory.
Several boxing experts believed Parker, thirty-one, should have been awarded the victory but the Derbyshire fighter suffered the second defeat of his 28-match career.
The Champion Earns Triumph in Slow Encounter
Buatsi's progress has stalled in recent years through promotional disputes and long spells of inactivity.
Once tipped as the next star of the British fight scene, he now stands trying to realize his potential - possibly in what seems like a final roll of the dice - under new promotional backing.
He began cautiously, with neither fighter prepared to be aggressive in a tentative opening few rounds.
The challenger, whose sole prior loss came at super middleweight against his former opponent in 2022 after damaging his hand mid-fight, was making just his second appearance at light-heavyweight.
By the middle rounds, Parker had kept it close, creating difficulties for the favorite, who utilized a tight guard to barely take the more effective periods.
The audience's tolerance wore thin amid constant clinching, with Parker falling to the floor various instances during close exchanges.
The underdog finished the stronger, but multiple periods were difficult to score. However, previous titleholder the boxing analyst - commentating on Dazn - had it significantly in favor for Parker, scoring for Buatsi just one round.
Buatsi advances, but with the likes of heavy hitter David Benavidez, and Russian star Bivol ruling the division, the journey to titles - on this evidence - still seems difficult.
Hatton Memorial Motivates All-Manchester Contest
In the co-main event, Arthur beat Bradley Rea by close verdict in a excellent all-Manchester fight to win the European light heavyweight belt.
The venue fell silent for a extremely emotional memorial before the fight as a bell ceremony tolled in honor of Manchester's own Ricky Hatton, who passed away aged 46 in last month.
It was the first major televised fight night in the urban center since Hatton's passing. As the concluding sound ended, the silence gave way to a chant of "only one Hatton".
The competition inside the ropes matched the feeling. Arthur was sent to the canvas by a powerful punch flush on the chin in the second round, getting up unsteadily to his feet on the eight count.
But the red-colored attire of Arthur soon came forward again. Across the ring, Rea - in rival City blue - was damaged soon, significant bruising developing under his face as the fighters traded powerful shots.
The challenger, 27, connected with strong blows but the champion, thirty-four, responded in kind with effective uppercuts as the pace hardly diminished over twelve rounds.
Arthur barely secured the result with scoring tallies of even score, 115-113 and 115-112, but the two athletes were relentless and courageous, everything their inspiration the legend stood for.
