British light-heavyweight Buatsi made a winning yet unimpressive beginning to life under new promoters with a unanimous decision over Zach Parker in Manchester.
The Olympic medal winner's activity level seemingly secured him a judges' verdict in a competitive ten-round bout at the boxing arena.
But Parker found success, connecting with powerful single shots in a match where the techniques failed to mesh, with frequent clinching spoiling the fight.
The officials judged it 96-94 to Buatsi, with the remaining official a 95-95.
"It wasn't my best showing but how do champions respond? They succeed," the victor commented in the ringside as he was faced negative reactions from the audience.
The Londoner bounced back after his maiden career setback - an memorable fight with his previous opponent in February - to earn a 20th career victory.
Several boxing experts thought Parker, thirty-one, should have been awarded the victory but the Derbyshire fighter endured the second loss of his 28-match career.
Buatsi Earns Win in Slow Match
The fighter's advancement has plateaued in recent times through contract problems and long spells of inactivity.
Earlier forecast as the next star of UK boxing, he now stands trying to achieve expectations - perhaps in what feels like a final roll of the dice - under recent support.
He began cautiously, with neither fighter ready to overcommit in a cagey opening few rounds.
The challenger, whose single earlier setback came at the lower weight class against John Ryder in 2022 after suffering a hand injury mid-fight, was making just his second appearance at light heavyweight.
By the halfway stage, the underdog had made it competitive, causing problems for the favorite, who worked behind a solid defense to edge the better rounds.
The spectators' acceptance decreased because of regular grabbing, with the challenger going down various instances during clinches.
The underdog finished the stronger, but multiple periods were difficult to score. However, former world champion Carl Frampton - providing analysis for the broadcast network - had it significantly in favor for the challenger, scoring for Buatsi just only one stanza.
The victor progresses, but with the caliber of power puncher Benavidez, and Russian star Bivol leading the category, the journey to titles - judging by this showing - still appears challenging.
Ricky Hatton Memorial Fuels All-Manchester Battle
In the secondary fight, Arthur beat Bradley Rea by split-decision in a excellent local rivalry battle to win the European light heavyweight title.
The stadium grew hushed for a profoundly moving memorial ahead of the contest as a bell ceremony rang in memory of Manchester's own Hatton, who passed away 46 years old in last month.
It was the first major televised match card in the location since the passing of Hatton. As the last bell faded, the quiet became a roar of "there's only one Hatton".
The competition inside the ropes reflected the sentiment. The eventual winner was knocked down by a significant blow squarely on the jaw in the early round, getting up unsteadily to his position on the referee's count.
But the traditional red shorts of the fighter soon came forward again. From the other corner, the opponent - in rival City blue - was marked up quickly, noticeable damage appearing under his face as the fighters landed punishing blows.
Rea, 27, delivered effective strikes but Arthur, thirty-four, matched the intensity with stinging uppercuts as the action seldom decreased over the full distance.
Arthur narrowly won the verdict with official scores of draw, 115-113 and clearer margin, but both fighters were relentless and full of heart, everything their idol Hatton represented.
