British light-heavyweight Buatsi made a winning yet disappointing start to his career under recent management with a decision win over Zach Parker in Manchester.
The Olympic bronze medallist's punch output appeared to earn him a split decision in a close 10-round fight at the Co-op Live Arena.
But the challenger had his moments, delivering effective single shots in a contest where the approaches never quite clicked, with frequent clinching disrupting the contest.
The scoring judges had it 96-94 to the winner, with the final judge a 95-95 draw.
"It wasn't my greatest display but how do champions respond? They prevail," the victor said in the ring as he was greeted with disapproval from the audience.
The Londoner bounced back after his initial pro loss - an epic battle with his previous opponent in February - to earn a 20th career victory.
Several boxing experts thought Parker, 31, merited the win but the British boxer suffered the second setback of his 28-fight career.
Buatsi Earns Victory in Dull Affair
Buatsi's progress has plateaued in recent times through contract problems and considerable time of inactivity.
Once tipped as the next star of British boxing, he now is positioned trying to achieve expectations - maybe in what seems like a ultimate opportunity - under recent support.
He opened tentatively, with both competitors ready to take risks in a cagey opening few rounds.
The challenger, whose only previous defeat came at super-middleweight against John Ryder in 2022 after suffering a hand injury during the bout, was participating in his second fight at light-heavyweight.
By the middle rounds, Parker had kept it close, making life awkward for the favorite, who utilized a solid defense to narrowly win the cleaner periods.
The spectators' acceptance diminished because of constant clinching, with the challenger going down various instances during grappling.
The underdog finished the stronger, but multiple periods were difficult to score. However, ex-champion the boxing analyst - providing analysis for Dazn - had it strongly leaning for Parker, scoring for Buatsi just a single round.
The victor advances, but with the likes of heavy hitter Benavidez, and Russian star Bivol ruling the division, the journey to titles - judging by this showing - still looks steep.
Hatton Homage Fuels Manchester Derby Battle
In the secondary fight, Lyndon Arthur beat Rea by divided decision in a excellent all-Manchester fight to capture the continental title.
The arena grew hushed for a profoundly moving tribute ahead of the contest as ten bells sounded in remembrance of Manchester's own Ricky Hatton, who passed away aged 46 in September.
It was the first major televised match card in the urban center since Hatton's death. As the final chime disappeared, the silence transitioned to a chant of "only one Ricky Hatton".
The competition within the ring reflected the sentiment. Arthur was knocked down by a significant blow directly to the jaw in the initial stage, standing uncertainly to his footing on the eight count.
But the Manchester United-red shorts of Arthur soon pressed ahead again. On the opposite side, the opponent - in rival City blue - was marked up quickly, noticeable damage developing under his orbital area as the duo landed powerful shots.
The challenger, twenty-seven, connected with strong blows but the champion, 34, matched the intensity with powerful upward punches as the pace seldom decreased over 12 rounds.
The victor barely secured the result with judges scorecards of 114-114, close margin and clearer margin, but both fighters were persistent and full of heart, exactly what their idol Hatton stood for.
