UK light-heavyweight Buatsi secured a victory yet underwhelming start to his career under fresh promotional backing with a unanimous decision over Zach Parker in Manchester.
The Olympic bronze medallist's punch output seemingly secured him a majority decision in a tight 10-round fight at the Co-op Live Arena.
But the challenger had his moments, delivering effective clean blows in a contest where the techniques never quite clicked, with frequent clinching marring the contest.
The scoring judges had it 96-94 in favor to Buatsi, with the third a 95-95.
"It wasn't my best showing but what do champions do? They prevail," Buatsi stated in the arena as he was faced disapproval from the crowd.
The Londoner bounced back after his first professional defeat - an epic battle with his previous opponent in February - to claim a twentieth professional win.
Various analysts felt the challenger, thirty-one, merited the victory but the British boxer suffered the second defeat of his 28-fight career.
Buatsi Earns Victory in Slow Affair
His career development has plateaued in the past few years through contract problems and extended periods of inactivity.
Earlier forecast as the next star of British boxing, he now stands trying to realize his potential - possibly in what seems like a last chance - under recent support.
He began cautiously, with both competitors prepared to take risks in a calculated opening few rounds.
The challenger, whose sole prior loss came at super middleweight against his former opponent in 2022 after suffering a hand injury in the contest, was making just his second fight at light-heavyweight.
By the halfway stage, Parker had stayed in contention, causing problems for Buatsi, who utilized a solid defense to barely take the cleaner periods.
The audience's tolerance wore thin during frequent holding, with Parker going down various instances during grappling.
The underdog finished the stronger, but many rounds were difficult to score. However, previous titleholder the boxing analyst - providing analysis for Dazn - had it particularly wide for the challenger, scoring for Buatsi just a single round.
The victor moves on, but with the caliber of power puncher Benavidez, and Eastern European fighter Dmitry Bivol ruling the division, the journey to titles - on this evidence - still seems difficult.
Ricky Hatton Memorial Fuels Local Rivalry Contest
In the co-main event, Arthur overcame Bradley Rea by split-decision in a excellent local rivalry contest to capture the European light-heavyweight championship.
The arena fell silent for a deeply poignant memorial before the fight as 10 bells tolled in memory of local hero Ricky Hatton, who succumbed 46 years old in September.
It was the first major televised match card in the location since the passing of Hatton. As the final chime disappeared, the stillness gave way to a roar of "there's just one Hatton".
The competition within the ring reflected the feeling. The eventual winner was sent to the canvas by a left hook squarely on the jaw in the initial stage, getting up unsteadily to his feet on the referee's count.
But the traditional red equipment of the fighter soon pressed ahead again. Across the ring, Rea - in rival City blue - was marked up early, significant bruising forming under his face as the duo landed hard punches.
The challenger, twenty-seven, delivered effective strikes but Arthur, 34, responded in kind with powerful upward punches as the intensity seldom decreased over the full distance.
The victor edged the decision with scoring tallies of 114-114, close margin and wider gap, but both fighters were determined and full of heart, exactly what their inspiration the legend represented.
