British light heavyweight Buatsi earned a win yet disappointing start to life under fresh promotional backing with a points victory over Zach Parker in the Manchester arena.
The Olympic medal winner's activity level likely gained him a split decision in a competitive 10-round fight at the Manchester venue.
But the challenger landed significant shots, landing some telling clean blows in a contest where the approaches didn't complement each other, with frequent clinching spoiling the fight.
Two judges judged it 96-94 in favor to Buatsi, with the third a 95-95.
"It wasn't my finest display but what do champions do? They win," the victor stated in the ringside as he was greeted with disapproval from the crowd.
The Londoner returned to winning ways after his first professional defeat - an thrilling contest with Callum Smith in February - to secure a 20th pro success.
Some ringside observers felt Parker, 31, should have been awarded the win but the British boxer experienced the second loss of his 28-match professional journey.
The Champion Secures Victory in Dull Encounter
His career development has plateaued in recent years through promotional disputes and considerable time of lack of fights.
Once tipped as the rising talent of UK boxing, he now finds himself trying to achieve expectations - maybe in what appears to be a last chance - under recent support.
He began cautiously, with both competitors willing to be aggressive in a cagey initial rounds.
The challenger, whose only previous defeat came at super middleweight against his former opponent in 2022 after breaking his hand mid-fight, was making just his second fight at the higher weight class.
By the halfway stage, the underdog had made it competitive, causing problems for Buatsi, who worked behind a protective stance to narrowly win the cleaner rounds.
The spectators' acceptance diminished amid regular grabbing, with the challenger going down multiple occasions during grappling.
The underdog closed well, but many rounds were difficult to score. Nevertheless, former world champion Carl Frampton - working with Dazn - had it particularly wide for the challenger, scoring for Buatsi just only one stanza.
The victor progresses, but with the presence of hard hitter Benavidez, and Russian star Dmitry Bivol ruling the division, the road to world glory - based on this performance - still looks steep.
Hatton Tribute Inspires All-Manchester Contest
In the secondary fight, Arthur beat Bradley Rea by divided decision in a outstanding local rivalry contest to win the European light-heavyweight belt.
The stadium fell silent for a deeply poignant homage ahead of the contest as ten bells sounded in honor of the city's native Hatton, who succumbed aged 46 in September.
It was the initial significant broadcast fight night in the location since Hatton's death. As the last bell faded, the silence gave way to a roar of "there's only one Hatton".
The action inside the ropes equaled the emotion. Arthur was knocked down by a left hook directly to the chin in the early round, getting up unsteadily to his position on the eight count.
But the traditional red attire of Arthur soon pressed ahead again. From the other corner, the opponent - in opposing blue - was marked up soon, heavy swelling developing under his eye as the fighters exchanged punishing blows.
The challenger, twenty-seven, landed power punches but Arthur, 34, fought fire with fire with effective uppercuts as the pace hardly diminished over twelve rounds.
The victor edged the decision with scoring tallies of draw, narrow lead and wider gap, but both fighters were determined and courageous, everything their inspiration Hatton embodied.
