British light-heavyweight Buatsi earned a win yet underwhelming beginning to his career under new promoters with a unanimous decision over Zach Parker in the Manchester arena.
The Olympic bronze medallist's work rate seemingly secured him a judges' verdict in a tight ten-round contest at the boxing arena.
But the challenger found success, delivering effective individual punches in a contest where the techniques failed to mesh, with constant grabbing spoiling the fight.
The scoring judges scored it 96-94 in favor to the winner, with the final judge a 95-95 draw.
"It wasn't my greatest display but how do champions respond? They succeed," Buatsi stated in the arena as he was faced negative reactions from the audience.
The Londoner bounced back after his maiden career setback - an thrilling contest with Callum Smith in February - to claim a 20th pro success.
Several boxing experts thought the challenger, 31, deserved the win but the British boxer endured the second setback of his 28-match professional journey.
Buatsi Claims Triumph in Slow Affair
The fighter's advancement has slowed in recent times through management issues and extended periods of inactivity.
Previously predicted as the rising talent of UK boxing, he now stands trying to fulfil that early promise - perhaps in what seems like a ultimate opportunity - under new promotional backing.
He opened tentatively, with both competitors willing to overcommit in a cagey opening few rounds.
Parker, whose single earlier setback came at super-middleweight against his former opponent in 2022 after damaging his hand mid-fight, was competing in only his second bout at light-heavyweight.
By the halfway stage, Parker had kept it close, making life awkward for the favorite, who worked behind a protective stance to narrowly win the better rounds.
The spectators' acceptance diminished during constant clinching, with Parker falling to the floor multiple occasions during clinches.
Parker ended stronger, but multiple periods were difficult to score. Although, ex-champion the boxing analyst - providing analysis for the broadcast network - had it significantly in favor for the challenger, scoring for Buatsi just one round.
Buatsi advances, but with the likes of hard hitter Benavidez, and Russian champion Dmitry Bivol leading the category, the path to championship success - on this evidence - still looks steep.
Ricky Hatton Tribute Motivates All-Manchester Fight
In the secondary fight, Lyndon Arthur defeated Rea by close verdict in a terrific Manchester vs Manchester battle to capture the European light heavyweight title.
The venue became quiet for a profoundly moving memorial before the fight as 10 bells sounded in memory of Manchester's own Ricky Hatton, who died aged 46 in last month.
It was the premier televised fight night in the location since the passing of Hatton. As the final chime faded, the stillness became a roar of "only one Ricky Hatton".
The action inside the ropes reflected the feeling. Arthur was floored by a left hook squarely on the chin in the initial stage, getting up unsteadily to his position on the referee's count.
But the traditional red attire of the fighter soon pressed ahead again. On the opposite side, the opponent - in competitive blue - was marked up early, significant bruising appearing under his face as the pair landed powerful shots.
Rea, twenty-seven, delivered effective strikes but Arthur, thirty-four, matched the intensity with stinging uppercuts as the action hardly diminished over twelve rounds.
The victor barely secured the decision with scoring tallies of even score, close margin and clearer margin, but the two athletes were determined and brave, everything their inspiration the legend embodied.
