British light-heavyweight Buatsi secured a victory yet disappointing start to life under recent management with a points victory over Zach Parker in Manchester.
The Olympic medal winner's punch output seemingly secured him a split decision in a competitive ten-round fight at the boxing arena.
But Parker found success, landing some telling single shots in a fight where the styles didn't complement each other, with frequent clinching marring the action.
The officials had it 96-94 in favor to the winner, with the remaining official a 95-95.
"It wasn't my best showing but what defines champions? They win," Buatsi stated in the ring as he was met by negative reactions from the audience.
The British fighter bounced back after his maiden career setback - an thrilling contest with Callum Smith in February - to secure a 20th pro success.
Various analysts felt the challenger, 31, deserved the victory but the contender experienced the second defeat of his 28-bout career.
The Champion Secures Triumph in Dull Affair
Buatsi's progress has stalled in recent years through management issues and considerable time of lack of fights.
Earlier forecast as the future of the British fight scene, he now is positioned trying to fulfil that early promise - maybe in what feels like a final roll of the dice - under recent support.
He started carefully, with both competitors ready to overcommit in a tentative initial rounds.
The challenger, whose sole prior loss came at super middleweight against John Ryder in 2022 after damaging his hand in the contest, was participating in his second fight at light heavyweight.
By the middle rounds, Parker had kept it close, causing problems for the favorite, who worked behind a solid defense to barely take the more effective stanzas.
The audience's tolerance decreased because of regular grabbing, with Parker slipping to the canvas several times during grappling.
The underdog finished the stronger, but multiple periods were difficult to score. Although, previous titleholder the boxing analyst - working with Dazn - had it significantly in favor for Parker, scoring for Buatsi just one round.
Buatsi progresses, but with the likes of hard hitter Benavidez, and Russian champion Bivol dominating the weight class, the path to championship success - based on this performance - still seems difficult.
Ricky Hatton Homage Motivates Manchester Derby Contest
In the secondary fight, Arthur overcame Rea by divided decision in a outstanding all-Manchester contest to win the European light heavyweight title.
The venue became quiet for a profoundly moving tribute ahead of the contest as 10 bells rang in memory of the city's native Ricky Hatton, who died at age 46 in last month.
It was the first major televised boxing event in the location since Hatton's death. As the last bell ended, the silence gave way to a shout of "only one Ricky Hatton".
The action inside the ropes equaled the sentiment. The eventual winner was knocked down by a significant blow directly to the face in the initial stage, rising shakily to his position on the count of eight.
But the traditional red attire of the fighter soon pressed ahead again. Across the ring, Rea - in opposing blue - was marked up quickly, significant bruising developing under his eye as the pair landed hard punches.
The challenger, twenty-seven, landed power punches but Arthur, thirty-four, matched the intensity with stinging uppercuts as the intensity hardly diminished over twelve rounds.
Arthur edged the decision with judges scorecards of 114-114, 115-113 and clearer margin, but the two athletes were persistent and full of heart, exactly what their hero the legend stood for.
