UK light-heavyweight Buatsi made a winning yet disappointing beginning to life under new promoters with a unanimous decision over Zach Parker in the Manchester arena.
The Olympic medal winner's work rate seemingly secured him a split decision in a close 10-round fight at the Manchester venue.
But Parker had his moments, connecting with powerful single shots in a fight where the techniques didn't complement each other, with excessive holding marring the fight.
The scoring judges scored it 96-94 in favor to the winner, with the final judge a 95-95.
"It wasn't my finest showing but what defines champions? They succeed," Buatsi commented in the ringside as he was met by negative reactions from the crowd.
The Londoner got back to winning after his maiden career setback - an thrilling contest with his previous opponent in last winter - to earn a 20th career victory.
Several boxing experts believed the challenger, 31, should have been awarded the decision but the Derbyshire fighter endured the second loss of his 28-match career.
The Champion Claims Triumph in Dull Encounter
Buatsi's progress has stalled in recent times through management issues and considerable time of inactivity.
Earlier forecast as the rising talent of British boxing, he now is positioned trying to realize his potential - perhaps in what appears to be a final roll of the dice - under new promotional backing.
He began cautiously, with neither fighter ready to take risks in a cagey early stages.
The challenger, whose only previous defeat came at super middleweight against John Ryder in 2022 after damaging his hand in the contest, was making just his second fight at light-heavyweight.
By the halfway stage, the underdog had made it competitive, creating difficulties for Buatsi, who operated with a protective stance to narrowly win the more effective rounds.
The spectators' acceptance decreased because of frequent holding, with Parker falling to the floor various instances during grappling.
Parker closed well, but multiple periods were hard to judge. Although, ex-champion Carl Frampton - commentating on Dazn - had it strongly leaning for the challenger, giving Buatsi just a single round.
The victor moves on, but with the caliber of power puncher Benavidez, and Russian champion Bivol dominating the weight class, the journey to titles - judging by this showing - still looks steep.
Hatton Memorial Motivates Local Rivalry Fight
In the secondary fight, Lyndon Arthur beat Bradley Rea by divided decision in a outstanding Manchester vs Manchester fight to capture the European light-heavyweight belt.
The venue grew hushed for a profoundly moving memorial before the fight as ten bells tolled in memory of local hero Ricky Hatton, who passed away 46 years old in September.
It was the premier televised match card in the urban center since Hatton's death. As the last bell faded, the quiet became a chant of "there's just one Ricky Hatton".
The competition inside the ropes reflected the emotion. The eventual winner was floored by a powerful punch directly to the face in the second round, getting up unsteadily to his position on the count of eight.
But the red-colored equipment of the fighter soon advanced again. Across the ring, Rea - in opposing blue - was damaged quickly, heavy swelling developing under his eye as the duo traded hard punches.
Rea, twenty-seven, delivered effective strikes but Arthur, thirty-four, responded in kind with powerful upward punches as the intensity seldom decreased over twelve rounds.
The victor barely secured the result with official scores of 114-114, 115-113 and 115-112, but the two athletes were relentless and courageous, everything their hero Hatton embodied.
