British light heavyweight Buatsi secured a victory yet disappointing start to his career under fresh promotional backing with a points victory over Zach Parker in the Manchester arena.
The Olympic bronze medallist's work rate appeared to earn him a judges' verdict in a competitive 10-round bout at the Co-op Live Arena.
But Parker found success, landing some telling clean blows in a fight where the approaches failed to mesh, with frequent clinching marring the action.
The scoring judges had it 96-94 for to the winner, with the third a 95-95.
"It wasn't my best performance but how do champions respond? They win," Buatsi commented in the arena as he was faced disapproval from the audience.
The Londoner returned to winning ways after his maiden career setback - an epic battle with Callum Smith in last winter - to claim a twentieth professional win.
Several boxing experts felt Parker, thirty-one, should have been awarded the decision but the British boxer suffered the second defeat of his 28-match career.
Buatsi Claims Victory in Uneventful Affair
His career development has plateaued in recent times through contract problems and extended periods of inactivity.
Earlier forecast as the next star of the British fight scene, he now stands trying to fulfil that early promise - possibly in what seems like a final roll of the dice - under fresh management.
He began cautiously, with the two boxers ready to be aggressive in a calculated initial rounds.
The challenger, whose sole prior loss came at the lower weight class against his former opponent in 2022 after breaking his hand mid-fight, was participating in his second bout at light-heavyweight.
By the middle rounds, the underdog had kept it close, making life awkward for Buatsi, who utilized a solid defense to edge the cleaner rounds.
The spectators' acceptance diminished during regular grabbing, with Parker slipping to the canvas various instances during grappling.
Parker closed well, but many rounds were difficult to score. Nevertheless, previous titleholder the boxing analyst - providing analysis for the broadcast network - had it particularly wide for the challenger, awarding Buatsi just a single round.
The victor advances, but with the likes of power puncher Benavidez, and Russian star Dmitry Bivol dominating the weight class, the journey to titles - based on this performance - still seems difficult.
Hatton Homage Fuels All-Manchester Contest
In the secondary fight, Arthur defeated Rea by close verdict in a terrific all-Manchester contest to win the European light heavyweight title.
The arena grew hushed for a extremely emotional tribute before the fight as a bell ceremony tolled in memory of the city's native Ricky Hatton, who passed away aged 46 in September.
It was the initial significant broadcast fight night in the city since the passing of Hatton. As the concluding sound disappeared, the silence transitioned to a shout of "there's just one Ricky Hatton".
The competition inside the ropes matched the feeling. The eventual winner was sent to the canvas by a powerful punch squarely on the jaw in the initial stage, rising shakily to his feet on the count of eight.
But the Manchester United-red shorts of Arthur soon advanced again. On the opposite side, Rea - in opposing blue - was marked up early, significant bruising appearing under his orbital area as the fighters landed punishing blows.
The challenger, twenty-seven, landed power punches but Arthur, thirty-four, fought fire with fire with powerful upward punches as the action rarely dropped over twelve rounds.
Arthur barely secured the decision with judges scorecards of even score, 115-113 and wider gap, but each competitor were determined and full of heart, all the qualities their hero Hatton embodied.
