British light-heavyweight Buatsi earned a win yet unimpressive start to life under fresh promotional backing with a unanimous decision over Zach Parker in the Manchester arena.
The Olympic medal winner's punch output seemingly secured him a split decision in a tight 10-round contest at the Manchester venue.
But Parker found success, landing some telling individual punches in a fight where the approaches never quite clicked, with frequent clinching spoiling the fight.
The officials judged it 96-94 in favor to the winner, with the third a even score.
"It wasn't my best performance but how do champions respond? They win," the victor said in the ringside as he was greeted with disapproval from the crowd.
The Londoner got back to winning after his maiden career setback - an memorable fight with his previous opponent in last winter - to earn a 20th career victory.
Various analysts believed Parker, 31, should have been awarded the victory but the contender experienced the second setback of his 28-match professional journey.
Buatsi Earns Triumph in Dull Encounter
Buatsi's progress has stalled in recent years through management issues and long spells of lack of fights.
Once tipped as the next star of British boxing, he now stands trying to achieve expectations - perhaps in what appears to be a ultimate opportunity - under recent support.
He began cautiously, with the two boxers ready to overcommit in a tentative initial rounds.
The challenger, whose single earlier setback came at super middleweight against John Ryder in two years ago after breaking his hand mid-fight, was making just his second appearance at light-heavyweight.
By the middle rounds, the underdog had made it competitive, causing problems for the favorite, who utilized a protective stance to barely take the more effective periods.
The audience's tolerance wore thin during regular grabbing, with the challenger falling to the floor several times during close exchanges.
The underdog closed well, but many rounds were hard to judge. Although, former world champion Carl Frampton - commentating on Dazn - had it particularly wide for Parker, giving Buatsi just only one stanza.
Buatsi moves on, but with the likes of heavy hitter Benavidez, and Eastern European fighter Bivol leading the category, the journey to titles - based on this performance - still looks steep.
Ricky Hatton Tribute Fuels All-Manchester Battle
In the co-main event, Arthur beat Rea by divided decision in a terrific all-Manchester battle to win the European light-heavyweight title.
The stadium fell silent for a extremely emotional memorial prior to the bout as ten bells rang in remembrance of the city's native Hatton, who passed away at age 46 in last month.
It was the first major televised match card in the city since Hatton's death. As the last bell faded, the stillness transitioned to a roar of "there's only one Hatton".
The competition inside the ropes equaled the sentiment. The eventual winner was floored by a powerful punch flush on the face in the initial stage, getting up unsteadily to his feet on the referee's count.
But the red-colored attire of the fighter soon came forward again. On the opposite side, Rea - in rival City blue - was injured soon, heavy swelling forming under his orbital area as the duo landed punishing blows.
The challenger, 27, landed power punches but Arthur, thirty-four, fought fire with fire with stinging uppercuts as the pace hardly diminished over the full distance.
Arthur barely secured the decision with official scores of draw, 115-113 and clearer margin, but each competitor were persistent and brave, exactly what their hero the legend represented.
