UK light heavyweight Buatsi made a winning yet disappointing beginning to his career under new promoters with a decision win over Zach Parker in Manchester.
The Olympic medal winner's activity level seemingly secured him a split decision in a tight ten-round fight at the Co-op Live Arena.
But Parker had his moments, delivering effective single shots in a fight where the styles never quite clicked, with frequent clinching disrupting the fight.
The officials scored it 96-94 for to the winner, with the third a 95-95.
"It wasn't my best performance but what defines champions? They prevail," the victor commented in the arena as he was faced boos from the spectators.
The British fighter returned to winning ways after his maiden career setback - an memorable fight with his previous opponent in February - to secure a 20th pro success.
Several boxing experts felt the challenger, 31, deserved the victory but the British boxer endured the second defeat of his 28-bout career.
Buatsi Earns Triumph in Slow Affair
Buatsi's progress has slowed in recent years through contract problems and long spells of inactivity.
Once tipped as the next star of British boxing, he now finds himself trying to achieve expectations - possibly in what appears to be a ultimate opportunity - under fresh management.
He began cautiously, with neither fighter willing to be aggressive in a cagey early stages.
The challenger, whose sole prior loss came at super-middleweight against his former opponent in 2022 after breaking his hand during the bout, was competing in only his second bout 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 more effective periods.
The crowd's patience diminished amid constant clinching, with Parker going down various instances during close exchanges.
The underdog ended stronger, but multiple periods were difficult to score. Although, former world champion Carl Frampton - providing analysis for Dazn - had it significantly in favor for Parker, awarding Buatsi just a single round.
Buatsi moves on, but with the caliber of hard hitter Benavidez, and Russian champion Dmitry Bivol ruling the division, the path to championship success - judging by this showing - still seems difficult.
Hatton Tribute Motivates All-Manchester Battle
In the supporting bout, Lyndon Arthur defeated Rea by divided decision in a outstanding all-Manchester contest to secure the European light-heavyweight championship.
The arena became quiet for a deeply poignant tribute prior to the bout as a bell ceremony tolled in memory of Manchester's own Hatton, who died 46 years old in recently.
It was the first major televised fight night in the city since Hatton's passing. As the last bell faded, the stillness transitioned to a shout of "there's only one Ricky Hatton".
The fighting inside the ropes matched the emotion. The eventual winner was knocked down by a left hook squarely on the chin in the early round, rising shakily to his position on the eight count.
But the traditional red equipment of Arthur soon advanced again. Across the ring, Rea - in opposing blue - was marked up quickly, noticeable damage developing under his eye as the fighters landed punishing blows.
The challenger, twenty-seven, connected with strong blows but Arthur, thirty-four, matched the intensity with effective uppercuts as the intensity seldom decreased over the full distance.
The victor edged the decision with official scores of draw, narrow lead and wider gap, but the two athletes were persistent and full of heart, exactly what their inspiration the legend stood for.
