British light heavyweight Buatsi earned a win yet disappointing start to life under fresh promotional backing with a points victory over Zach Parker in Manchester.
The Olympic bronze medallist's activity level appeared to earn him a split decision in a competitive ten-round fight at the Co-op Live Arena.
But the challenger landed significant shots, connecting with powerful single shots in a match where the approaches failed to mesh, with excessive holding spoiling the action.
The scoring judges judged it 96-94 for to the winner, with the final judge a 95-95 draw.
"It wasn't my best showing but what defines champions? They win," the victor said in the arena as he was faced negative reactions from the crowd.
The British fighter bounced back after his first professional defeat - an epic battle with his previous opponent in February - to earn a 20th career victory.
Various analysts felt Parker, thirty-one, merited the victory but the Derbyshire fighter suffered the second setback of his 28-match professional journey.
Buatsi Earns Victory in Slow Match
His career development has plateaued in recent times through promotional disputes and long spells of inactivity.
Earlier forecast as the rising talent of UK boxing, he now is positioned trying to fulfil that early promise - perhaps in what feels like a last chance - under new promotional backing.
He opened tentatively, with neither fighter willing to take risks in a calculated opening few rounds.
Parker, whose sole prior loss came at the lower weight class against John Ryder in 2022 after breaking his hand mid-fight, was participating in his second bout at light heavyweight.
By the middle rounds, Parker had stayed in contention, creating difficulties for the favorite, who utilized a solid defense to edge the more effective rounds.
The spectators' acceptance wore thin amid frequent holding, with Parker slipping to the canvas various instances during clinches.
Parker ended stronger, but many rounds were difficult to score. Although, previous titleholder the boxing analyst - providing analysis for the broadcast network - had it strongly leaning for Parker, scoring for Buatsi just only one stanza.
The victor advances, but with the presence of heavy hitter Benavidez, and Eastern European fighter Dmitry Bivol dominating the weight class, the path to championship success - on this evidence - still looks steep.
Ricky Hatton Memorial Motivates Manchester Derby Contest
In the secondary fight, Arthur beat Rea by split-decision in a outstanding all-Manchester contest to win the European light heavyweight championship.
The arena grew hushed for a extremely emotional memorial ahead of the contest as a bell ceremony rang in memory of Manchester's own Hatton, who died 46 years old in last month.
It was the first major televised match card in the urban center since Hatton's passing. As the concluding sound faded, the quiet gave way to a chant of "only one Hatton".
The fighting during the bout reflected the sentiment. The eventual winner was sent to the canvas by a significant blow directly to the chin in the second round, rising shakily to his position on the eight count.
But the traditional red equipment of Arthur soon pressed ahead again. Across the ring, Rea - in competitive blue - was damaged soon, significant bruising appearing under his eye as the fighters traded hard punches.
Rea, 27, landed power punches but the champion, 34, fought fire with fire with effective uppercuts as the action seldom decreased over the full distance.
Arthur narrowly won the verdict with official scores of even score, narrow lead and clearer margin, but each competitor were determined and brave, all the qualities their idol Hatton stood for.
