UK light-heavyweight Buatsi earned a win yet underwhelming start to life under new promoters with a decision win over Zach Parker in Manchester.
The Olympic medal winner's work rate seemingly secured him a judges' verdict in a close ten-round fight at the boxing arena.
But the challenger found success, connecting with powerful individual punches in a contest where the approaches didn't complement each other, with frequent clinching spoiling the fight.
The scoring judges scored it 96-94 to the winner, with the remaining official a 95-95.
"It wasn't my best display but what do champions do? They succeed," the victor said in the ringside as he was met by negative reactions from the audience.
The British fighter bounced back after his maiden career setback - an epic battle with his previous opponent in last winter - to secure a twentieth professional win.
Some ringside observers thought Parker, thirty-one, deserved the victory but the Derbyshire fighter endured the second defeat of his 28-bout career.
The Champion Claims Win in Dull Match
Buatsi's progress has slowed in recent years through contract problems and extended periods of lack of fights.
Earlier forecast as the next star of UK boxing, he now is positioned trying to achieve expectations - possibly in what feels like a final roll of the dice - under recent support.
He began cautiously, with neither fighter willing to take risks in a calculated initial rounds.
The challenger, whose sole prior loss came at the lower weight class against his former opponent in 2022 after suffering a hand injury in the contest, was competing in only his second bout at the higher weight class.
By the fight's midpoint, the underdog had stayed in contention, causing problems for Buatsi, who worked behind a protective stance to barely take the better rounds.
The spectators' acceptance decreased amid regular grabbing, with Parker falling to the floor multiple occasions during clinches.
The underdog closed well, but several stanzas were difficult to score. Although, former world champion Carl Frampton - providing analysis for the broadcast network - had it strongly leaning for the challenger, scoring for Buatsi just a single round.
Buatsi moves on, but with the caliber of hard hitter David Benavidez, and Russian star Dmitry Bivol dominating the weight class, the path to championship success - on this evidence - still appears challenging.
Ricky Hatton Homage Inspires Manchester Derby Battle
In the secondary fight, Arthur beat Rea by divided decision in a outstanding Manchester vs Manchester fight to secure the continental title.
The stadium fell silent for a profoundly moving memorial before the fight as a bell ceremony tolled in remembrance of Manchester's own Hatton, who succumbed at age 46 in last month.
It was the initial significant broadcast boxing event in the location since Hatton's passing. As the concluding sound faded, the silence gave way to a chant of "only one Ricky Hatton".
The competition within the ring matched the feeling. Arthur was sent to the canvas by a significant blow squarely on the face in the early round, standing uncertainly to his position on the count of eight.
But the Manchester United-red shorts of Arthur soon advanced again. Across the ring, Rea - in opposing blue - was damaged soon, significant bruising appearing under his orbital area as the duo landed powerful shots.
Rea, 27, delivered effective strikes but Arthur, thirty-four, matched the intensity with effective uppercuts as the intensity hardly diminished over twelve rounds.
The victor barely secured the result with official scores of 114-114, close margin and wider gap, but each competitor were persistent and courageous, everything their hero the legend embodied.
