British light-heavyweight Buatsi earned a win yet unimpressive beginning to life under new promoters with a points victory over Zach Parker in the Manchester arena.
The Olympic medal winner's punch output appeared to earn him a judges' verdict in a close 10-round contest at the Manchester venue.
But Parker had his moments, connecting with powerful clean blows in a fight where the techniques never quite clicked, with constant grabbing disrupting the action.
Two judges scored it 96-94 in favor to the winner, with the remaining official a even score.
"It wasn't my greatest showing but what defines champions? They win," Buatsi commented in the ring as he was faced negative reactions from the crowd.
The Londoner returned to winning ways after his first professional defeat - an thrilling contest with his previous opponent in February - to secure a 20th career victory.
Several boxing experts believed Parker, thirty-one, should have been awarded the victory but the contender suffered the second setback of his 28-fight career.
Buatsi Earns Triumph in Uneventful Encounter
His career development has plateaued in recent times through management issues and long spells of inactivity.
Once tipped as the rising talent of British boxing, he now finds himself trying to fulfil that early promise - maybe in what seems like a final roll of the dice - under fresh management.
He started carefully, with both competitors ready to take risks in a calculated early stages.
The challenger, whose sole prior loss came at super-middleweight against John Ryder in 2022 after damaging his hand mid-fight, was making just his second fight at the higher weight class.
By the middle rounds, Parker had stayed in contention, creating difficulties for Buatsi, who worked behind a solid defense to edge the cleaner periods.
The spectators' acceptance decreased during regular grabbing, with Parker slipping to the canvas several times during clinches.
Parker ended stronger, but multiple periods were difficult to score. However, former world champion the boxing analyst - commentating on the broadcast network - had it strongly leaning for the challenger, scoring for Buatsi just one round.
Buatsi progresses, but with the presence of heavy hitter Benavidez, and Russian star Dmitry Bivol ruling the division, the path to championship success - based on this performance - still looks steep.
Ricky Hatton Memorial Motivates Manchester Derby Contest
In the co-main event, Arthur beat Rea by close verdict in a outstanding all-Manchester fight to win the European light heavyweight belt.
The arena grew hushed for a profoundly moving tribute prior to the bout as 10 bells rang in remembrance of local hero Ricky Hatton, who died aged 46 in last month.
It was the initial significant broadcast boxing event in the city since Hatton's death. As the last bell disappeared, the stillness gave way to a roar of "only one Ricky Hatton".
The competition inside the ropes matched the sentiment. Arthur was knocked down by a powerful punch flush on the face in the early round, rising shakily to his feet on the referee's count.
But the traditional red attire of the fighter soon pressed ahead again. From the other corner, the opponent - in rival City blue - was marked up quickly, heavy swelling appearing under his orbital area as the pair exchanged hard punches.
Rea, twenty-seven, delivered effective strikes but the champion, 34, fought fire with fire with stinging uppercuts as the intensity rarely dropped over twelve rounds.
The victor edged the verdict with judges scorecards of draw, 115-113 and 115-112, but each competitor were persistent and full of heart, all the qualities their idol the legend stood for.
