British light heavyweight Buatsi made a winning yet disappointing beginning to his career under fresh promotional backing with a decision win over Zach Parker in Manchester.
The Olympic bronze medallist's work rate appeared to earn him a majority decision in a tight ten-round fight at the boxing arena.
But Parker found success, connecting with powerful single shots in a match where the styles didn't complement each other, with frequent clinching disrupting the fight.
The scoring judges scored it 96-94 in favor to the winner, with the remaining official a 95-95.
"It wasn't my finest performance but what do champions do? They prevail," Buatsi commented in the ringside as he was greeted with disapproval from the crowd.
The British fighter returned to winning ways after his maiden career setback - an thrilling contest with his previous opponent in last winter - to secure a 20th pro success.
Various analysts felt the challenger, thirty-one, should have been awarded the decision but the contender endured the second loss of his 28-fight career.
The Champion Secures Win in Dull Encounter
His career development has plateaued in recent years through promotional disputes and extended periods of inactivity.
Earlier forecast as the future of the British fight scene, he now is positioned trying to fulfil that early promise - possibly in what seems like a final roll of the dice - under recent support.
He started carefully, with the two boxers ready to overcommit in a cagey early stages.
The challenger, whose only previous defeat came at super middleweight against John Ryder in 2022 after breaking his hand mid-fight, was participating in his second appearance at the higher weight class.
By the fight's midpoint, the underdog had kept it close, causing problems for Buatsi, who utilized a protective stance to narrowly win the better stanzas.
The crowd's patience diminished during regular grabbing, with the challenger slipping to the canvas several times during close exchanges.
Parker closed well, but several stanzas were challenging to assess. Nevertheless, former world champion the boxing analyst - commentating on Dazn - had it significantly in favor for the challenger, giving Buatsi just only one stanza.
The victor progresses, but with the caliber of heavy hitter David Benavidez, and Russian star Bivol dominating the weight class, the road to world glory - on this evidence - still seems difficult.
Ricky Hatton Memorial Fuels Manchester Derby Contest
In the secondary fight, Arthur defeated Bradley Rea by close verdict in a terrific Manchester vs Manchester battle to capture the European light heavyweight belt.
The arena grew hushed for a deeply poignant tribute prior to the bout as ten bells rang in memory of Manchester's own Hatton, who died aged 46 in September.
It was the premier televised boxing event in the city since Hatton's death. As the concluding sound ended, the silence became a chant of "there's just one Hatton".
The competition within the ring equaled the feeling. The eventual winner was knocked down by a significant blow directly to the face in the initial stage, standing uncertainly to his footing on the referee's count.
But the traditional red attire of the fighter soon came forward again. From the other corner, the opponent - in rival City blue - was marked up quickly, significant bruising developing under his eye as the fighters landed punishing blows.
The challenger, twenty-seven, delivered effective strikes but Arthur, 34, matched the intensity with powerful upward punches as the action hardly diminished over 12 rounds.
Arthur barely secured the verdict with scoring tallies of 114-114, 115-113 and wider gap, but both fighters were persistent and brave, all the qualities their inspiration the legend stood for.
