UK light heavyweight Buatsi made a winning yet underwhelming start to life under fresh promotional backing with a decision win over Zach Parker in Manchester.
The Olympic bronze medallist's punch output seemingly secured him a judges' verdict in a close ten-round bout at the Manchester venue.
But Parker found success, landing some telling single shots in a match where the techniques failed to mesh, with frequent clinching marring the contest.
The scoring judges had it 96-94 for to Buatsi, with the final judge a 95-95.
"It wasn't my greatest showing but what do champions do? They succeed," the victor said in the ringside as he was met by disapproval from the spectators.
The British fighter got back to winning after his initial pro loss - an thrilling contest with his previous opponent in February - to earn a 20th career victory.
Some ringside observers believed the challenger, thirty-one, merited the decision but the contender experienced the second defeat of his 28-match career.
Buatsi Secures Win in Dull Encounter
The fighter's advancement has plateaued in the past few years through promotional disputes and long spells of inactivity.
Earlier forecast as the rising talent of the British fight scene, he now stands trying to achieve expectations - possibly in what feels like a ultimate opportunity - under new promotional backing.
He began cautiously, with both competitors willing to take risks in a calculated opening few rounds.
Parker, whose only previous defeat came at super middleweight against his former opponent in 2022 after suffering a hand injury during the bout, was participating in his second fight at light heavyweight.
By the halfway stage, the underdog had made it competitive, making life awkward for the favorite, who operated with a solid defense to narrowly win the better rounds.
The spectators' acceptance diminished because of frequent holding, with Parker going down various instances during close exchanges.
Parker closed well, but many rounds were difficult to score. Nevertheless, previous titleholder the boxing analyst - providing analysis for the broadcast network - had it particularly wide for Parker, awarding Buatsi just only one stanza.
Buatsi progresses, but with the likes of hard hitter Benavidez, and Russian champion Bivol dominating the weight class, the journey to titles - based on this performance - still looks steep.
Hatton Memorial Motivates Manchester Derby Fight
In the secondary fight, Lyndon Arthur overcame Bradley Rea by close verdict in a terrific local rivalry battle to win the continental title.
The stadium became quiet for a profoundly moving tribute before the fight as ten bells tolled in honor of the city's native Ricky Hatton, who died 46 years old in recently.
It was the premier televised boxing event in the location since Hatton's passing. As the concluding sound disappeared, the silence became a roar of "there's just one Ricky Hatton".
The competition during the bout equaled the emotion. The eventual winner was floored by a left hook flush on the face in the initial stage, standing uncertainly to his footing on the count of eight.
But the red-colored equipment of the fighter soon advanced again. From the other corner, Rea - in opposing blue - was damaged quickly, significant bruising forming under his eye as the pair exchanged hard punches.
The challenger, 27, delivered effective strikes but the champion, thirty-four, responded in kind with powerful upward punches as the action seldom decreased over the full distance.
The victor narrowly won the result with scoring tallies of draw, 115-113 and 115-112, but the two athletes were determined and courageous, all the qualities their hero the legend embodied.
