UK light-heavyweight Buatsi secured a victory yet disappointing beginning to his career under new promoters with a decision win over Zach Parker in the Manchester arena.
The Olympic bronze medallist's work rate likely gained him a judges' verdict in a competitive 10-round bout at the boxing arena.
But Parker had his moments, delivering effective single shots in a match where the styles failed to mesh, with frequent clinching spoiling the action.
The officials had it 96-94 for to the winner, with the third a even score.
"It wasn't my greatest performance but what do champions do? They succeed," the victor said in the ring as he was greeted with negative reactions from the spectators.
The British fighter bounced back after his initial pro loss - an memorable fight with his previous opponent in February - to earn a twentieth professional win.
Several boxing experts felt the challenger, thirty-one, merited the win but the contender endured the second setback of his 28-bout professional journey.
Buatsi Claims Triumph in Uneventful Affair
Buatsi's progress has slowed in recent times through promotional disputes and extended periods of inactivity.
Earlier forecast as the next star of British boxing, he now stands trying to fulfil that early promise - perhaps in what appears to be a ultimate opportunity - under new promotional backing.
He opened tentatively, with neither fighter willing to overcommit in a tentative initial rounds.
Parker, whose only previous defeat came at super-middleweight against his former opponent in 2022 after damaging his hand in the contest, was making just his second fight at the higher weight class.
By the halfway stage, the underdog had made it competitive, making life awkward for Buatsi, who worked behind a protective stance to barely take the more effective rounds.
The audience's tolerance wore thin during frequent holding, with Parker falling to the floor several times during close exchanges.
The underdog ended stronger, but many rounds were challenging to assess. Although, previous titleholder the boxing analyst - commentating on the broadcast network - had it significantly in favor for the challenger, giving Buatsi just one round.
Buatsi progresses, but with the likes of power puncher Benavidez, and Russian star Dmitry Bivol leading the category, the path to championship success - judging by this showing - still appears challenging.
Hatton Memorial Fuels All-Manchester Fight
In the co-main event, Lyndon Arthur overcame Bradley Rea by divided decision in a terrific Manchester vs Manchester contest to capture the European light-heavyweight championship.
The venue fell silent for a profoundly moving homage before the fight as ten bells tolled in remembrance of local hero Hatton, who passed away at age 46 in recently.
It was the premier televised boxing event in the city since Hatton's passing. As the last bell disappeared, the quiet gave way to a shout of "there's only one Ricky Hatton".
The competition inside the ropes matched the sentiment. Arthur was floored by a significant blow squarely on the face in the initial stage, getting up unsteadily to his feet on the count of eight.
But the traditional red attire of the fighter soon advanced again. On the opposite side, Rea - in rival City blue - was marked up soon, noticeable damage developing under his face as the fighters landed powerful shots.
Rea, 27, connected with strong blows but the champion, thirty-four, fought fire with fire with stinging uppercuts as the action rarely dropped over twelve rounds.
The victor narrowly won the result with official scores of 114-114, close margin and 115-112, but each competitor were relentless and courageous, exactly what their hero the legend embodied.
