UK light-heavyweight Buatsi secured a victory yet disappointing start to life under new promoters with a points victory over Zach Parker in the Manchester arena.
The Olympic medal winner's work rate seemingly secured him a judges' verdict in a close 10-round fight at the boxing arena.
But the challenger found success, landing some telling individual punches in a contest where the styles failed to mesh, with frequent clinching marring the action.
Two judges judged it 96-94 for to the winner, with the third a 95-95 draw.
"It wasn't my greatest performance but what defines champions? They win," the victor said in the arena as he was met by negative reactions from the audience.
The Londoner returned to winning ways after his initial pro loss - an epic battle with his previous opponent in last winter - to secure a twentieth professional win.
Various analysts thought the challenger, 31, merited the victory but the British boxer endured the second setback of his 28-bout career.
The Champion Secures Triumph in Uneventful Match
The fighter's advancement has slowed in the past few years through management issues and considerable time of inactivity.
Previously predicted as the rising talent of the British fight scene, he now stands trying to fulfil that early promise - perhaps in what seems like a final roll of the dice - under recent support.
He began cautiously, with the two boxers willing to take risks in a tentative initial rounds.
Parker, whose sole prior loss came at super middleweight against John Ryder in 2022 after suffering a hand injury in the contest, was competing in only his second fight at light heavyweight.
By the halfway stage, Parker had stayed in contention, causing problems for the favorite, who worked behind a solid defense to barely take the cleaner rounds.
The spectators' acceptance decreased because of constant clinching, with the challenger slipping to the canvas various instances during grappling.
The underdog finished the stronger, but many rounds were challenging to assess. Although, former world champion Carl Frampton - working with the broadcast network - had it particularly wide for Parker, scoring for Buatsi just a single round.
Buatsi advances, but with the caliber of heavy hitter Benavidez, and Russian star Bivol leading the category, the path to championship success - based on this performance - still appears challenging.
Ricky Hatton Tribute Motivates All-Manchester Battle
In the supporting bout, Arthur overcame Bradley Rea by divided decision in a excellent all-Manchester fight to capture the European light-heavyweight championship.
The stadium fell silent for a profoundly moving homage before the fight as a bell ceremony tolled in memory of the city's native Ricky Hatton, who passed away aged 46 in September.
It was the initial significant broadcast match card in the urban center since Hatton's passing. As the concluding sound faded, the quiet became a shout of "there's just one Ricky Hatton".
The action within the ring reflected the emotion. Arthur was floored by a powerful punch directly to the jaw in the early round, rising shakily to his position on the referee's count.
But the Manchester United-red attire of Arthur soon came forward again. On the opposite side, Rea - in competitive blue - was injured early, heavy swelling developing under his orbital area as the duo landed hard punches.
Rea, 27, connected with strong blows but the champion, 34, fought fire with fire with effective uppercuts as the pace hardly diminished over the full distance.
The victor barely secured the result with judges scorecards of 114-114, 115-113 and clearer margin, but both fighters were persistent and courageous, all the qualities their inspiration the legend stood for.
