UK light heavyweight Buatsi made a winning yet disappointing debut to life under new promoters with a points victory over Zach Parker in the Manchester arena.
The Olympic bronze medallist's punch output seemingly secured him a split decision in a close ten-round fight at the Manchester venue.
But Parker found success, connecting with powerful individual punches in a match where the approaches failed to mesh, with frequent clinching spoiling the action.
The scoring judges had it 96-94 to Buatsi, with the remaining official a 95-95.
"It wasn't my finest showing but what do champions do? They succeed," Buatsi commented in the ring as he was met by boos from the crowd.
The British fighter returned to winning ways after his initial pro loss - an thrilling contest with his previous opponent in February - to earn a twentieth professional win.
Various analysts felt Parker, 31, merited the victory but the contender endured the second setback of his 28-match career.
Buatsi Earns Triumph in Uneventful Encounter
Buatsi's progress has stalled in recent times through promotional disputes and long spells of inactivity.
Once tipped as the future of UK boxing, he now stands trying to fulfil that early promise - perhaps in what seems like a last chance - under new promotional backing.
He started carefully, with the two boxers ready to take risks in a calculated early stages.
The challenger, whose sole prior loss 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 fight's midpoint, Parker had stayed in contention, making life awkward for the favorite, who worked behind a solid defense to edge the better periods.
The audience's tolerance decreased because of frequent holding, with Parker falling to the floor multiple occasions during close exchanges.
The underdog ended stronger, but multiple periods were challenging to assess. However, previous titleholder Carl Frampton - working with the broadcast network - had it strongly leaning for the challenger, scoring for Buatsi just one round.
The victor moves on, but with the caliber of hard hitter Benavidez, and Russian champion Bivol ruling the division, the journey to titles - based on this performance - still seems difficult.
Ricky Hatton Tribute Inspires All-Manchester Battle
In the supporting bout, Lyndon Arthur beat Bradley Rea by divided decision in a excellent Manchester vs Manchester contest to secure the European light heavyweight belt.
The arena became quiet for a extremely emotional memorial prior to the bout as a bell ceremony tolled in remembrance of local hero Ricky Hatton, who died aged 46 in September.
It was the initial significant broadcast match card in the city since Hatton's death. As the last bell disappeared, the quiet became a shout of "there's just one Ricky Hatton".
The competition during the bout reflected the emotion. The eventual winner was knocked down by a left hook squarely on the jaw in the early round, getting up unsteadily to his footing on the eight count.
But the traditional red equipment of the fighter soon pressed ahead again. From the other corner, Rea - in opposing blue - was marked up soon, significant bruising developing under his face as the fighters traded powerful shots.
The challenger, 27, delivered effective strikes but Arthur, 34, fought fire with fire with stinging uppercuts as the action hardly diminished over the full distance.
The victor barely secured the verdict with judges scorecards of 114-114, narrow lead and clearer margin, but each competitor were persistent and brave, exactly what their inspiration Hatton represented.
