UK light heavyweight Buatsi earned a win yet underwhelming start to his career under fresh promotional backing with a unanimous decision over Zach Parker in Manchester.
The Olympic bronze medallist's activity level appeared to earn him a split decision in a close 10-round bout at the Co-op Live Arena.
But the challenger had his moments, connecting with powerful individual punches in a contest where the styles didn't complement each other, with frequent clinching spoiling the fight.
The officials scored it 96-94 to the winner, with the remaining official a even score.
"It wasn't my greatest display but what defines champions? They prevail," Buatsi stated in the ring as he was faced boos from the crowd.
The Londoner got back to winning after his first professional defeat - an epic battle with Callum Smith in last winter - to claim a 20th pro success.
Some ringside observers felt the challenger, 31, should have been awarded the win but the contender suffered the second defeat of his 28-match professional journey.
Buatsi Secures Win in Slow Affair
The fighter's advancement has plateaued in the past few years through management issues and extended periods of inactivity.
Once tipped as the future of British boxing, he now is positioned trying to fulfil that early promise - perhaps in what appears to be a ultimate opportunity - under fresh management.
He opened tentatively, with both competitors willing to take risks in a calculated opening few rounds.
The challenger, whose single earlier setback came at super middleweight against his former opponent in 2022 after suffering a hand injury mid-fight, was making just his second bout at light heavyweight.
By the fight's midpoint, Parker had kept it close, creating difficulties for the favorite, who operated with a protective stance to narrowly win the cleaner rounds.
The crowd's patience decreased because of regular grabbing, with Parker falling to the floor several times during grappling.
Parker closed well, but many rounds were challenging to assess. Although, ex-champion the boxing analyst - commentating on Dazn - had it particularly wide for Parker, awarding Buatsi just one round.
Buatsi advances, but with the presence of hard hitter Benavidez, and Russian champion Dmitry Bivol dominating the weight class, the path to championship success - on this evidence - still appears challenging.
Hatton Memorial Motivates Local Rivalry Battle
In the co-main event, Lyndon Arthur defeated Bradley Rea by close verdict in a terrific all-Manchester fight to capture the European light-heavyweight title.
The arena grew hushed for a extremely emotional memorial ahead of the contest as a bell ceremony sounded in remembrance of local hero Hatton, who died at age 46 in September.
It was the first major televised boxing event in the urban center since the passing of Hatton. As the last bell faded, the quiet gave way to a roar of "there's only one Ricky Hatton".
The action inside the ropes matched the sentiment. Arthur was knocked down by a powerful punch squarely on the face in the initial stage, standing uncertainly to his position on the eight count.
But the Manchester United-red equipment of Arthur soon pressed ahead again. Across the ring, the opponent - in competitive blue - was damaged early, noticeable damage developing under his face as the duo traded hard punches.
The challenger, 27, landed power punches but Arthur, thirty-four, fought fire with fire with powerful upward punches as the intensity seldom decreased over twelve rounds.
The victor barely secured the verdict with judges scorecards of draw, close margin and clearer margin, but both fighters were persistent and brave, everything their idol Hatton represented.
