UK light-heavyweight Buatsi earned a win yet unimpressive debut to his career under fresh promotional backing with a decision win over Zach Parker in Manchester.
The Olympic bronze medallist's activity level likely gained him a judges' verdict in a close ten-round contest at the Manchester venue.
But the challenger had his moments, delivering effective individual punches in a match where the techniques failed to mesh, with frequent clinching disrupting the contest.
The scoring judges scored it 96-94 in favor to the winner, with the remaining official a 95-95 draw.
"It wasn't my finest showing but what defines champions? They succeed," Buatsi said in the arena as he was greeted with boos from the crowd.
The Londoner bounced back after his maiden career setback - an epic battle with his previous opponent in February - to claim a 20th pro success.
Various analysts believed the challenger, 31, merited the win but the British boxer endured the second setback of his 28-bout career.
Buatsi Secures Triumph in Uneventful Encounter
Buatsi's progress has slowed in recent times through management issues and extended periods of inactivity.
Once tipped as the next star of British boxing, he now finds himself trying to fulfil that early promise - possibly in what feels like a last chance - under fresh management.
He started carefully, with both competitors ready to take risks in a tentative opening few rounds.
Parker, whose sole prior loss came at super-middleweight against his former opponent in 2022 after breaking his hand during the bout, was making just his second fight at the higher weight class.
By the halfway stage, Parker had kept it close, making life awkward for Buatsi, who worked behind a solid defense to edge the better rounds.
The audience's tolerance wore thin because of frequent holding, with Parker going down various instances during grappling.
The underdog finished the stronger, but multiple periods were difficult to score. Although, previous titleholder the boxing analyst - working with the broadcast network - had it strongly leaning for the challenger, scoring for Buatsi just only one stanza.
The victor progresses, but with the presence of heavy hitter Benavidez, and Russian champion Dmitry Bivol dominating the weight class, the journey to titles - based on this performance - still looks steep.
Hatton Memorial Inspires Manchester Derby Fight
In the supporting bout, Lyndon Arthur beat Bradley Rea by split-decision in a outstanding Manchester vs Manchester fight to win the European light-heavyweight championship.
The venue became quiet for a profoundly moving memorial ahead of the contest as 10 bells sounded in remembrance of local hero Hatton, who passed away 46 years old in last month.
It was the initial significant broadcast fight night in the location since Hatton's passing. As the final chime faded, the silence became a roar of "there's just one Hatton".
The action during the bout matched the feeling. Arthur was floored by a powerful punch squarely on the face in the initial stage, rising shakily to his position on the count of eight.
But the red-colored shorts of the fighter soon came forward again. From the other corner, Rea - in competitive blue - was damaged early, heavy swelling appearing under his eye as the fighters exchanged hard punches.
Rea, 27, connected with strong blows but the champion, 34, responded in kind with effective uppercuts as the pace seldom decreased over twelve rounds.
The victor narrowly won the verdict with official scores of draw, narrow lead and wider gap, but both fighters were relentless and full of heart, exactly what their hero Hatton stood for.
