British light-heavyweight Buatsi made a winning yet unimpressive debut 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 majority decision in a tight ten-round contest at the Co-op Live Arena.
But Parker found success, delivering effective clean blows in a fight where the styles failed to mesh, with constant grabbing spoiling the contest.
The officials had it 96-94 to Buatsi, with the remaining official a 95-95 draw.
"It wasn't my finest showing but what defines champions? They win," the victor commented in the arena as he was greeted with disapproval from the spectators.
The Londoner bounced back after his maiden career setback - an memorable fight with Callum Smith in last winter - to secure a 20th career victory.
Various analysts thought Parker, 31, should have been awarded the win but the British boxer suffered the second defeat of his 28-fight career.
The Champion Secures Win in Uneventful Encounter
His career development has slowed in recent times through promotional disputes and extended periods of inactivity.
Earlier forecast as the future of British boxing, he now is positioned trying to fulfil that early promise - possibly in what seems like a ultimate opportunity - under new promotional backing.
He opened tentatively, with the two boxers willing to overcommit in a cagey early stages.
The challenger, whose single earlier setback came at the lower weight class against John Ryder in 2022 after suffering a hand injury in the contest, was making just his second fight at light-heavyweight.
By the fight's midpoint, the underdog had made it competitive, causing problems for the favorite, who worked behind a solid defense to narrowly win the cleaner periods.
The spectators' acceptance diminished during regular grabbing, with Parker going down various instances during grappling.
Parker ended stronger, but several stanzas were challenging to assess. Although, former world champion the boxing analyst - commentating on Dazn - had it particularly wide for Parker, awarding Buatsi just only one stanza.
The victor advances, but with the presence of heavy hitter David Benavidez, and Russian champion Dmitry Bivol leading the category, the journey to titles - judging by this showing - still seems difficult.
Ricky Hatton Tribute Fuels Local Rivalry Fight
In the co-main event, Arthur beat Bradley Rea by split-decision in a outstanding Manchester vs Manchester battle to capture the European light-heavyweight title.
The stadium grew hushed for a profoundly moving memorial before the fight as ten bells rang in remembrance of the city's native Hatton, who died at age 46 in last month.
It was the premier televised match card in the city since Hatton's passing. As the last bell faded, the quiet became a roar of "there's just one Hatton".
The competition within the ring matched the sentiment. Arthur was knocked down by a powerful punch squarely on the face in the second round, rising shakily to his footing on the referee's count.
But the Manchester United-red attire of Arthur soon came forward again. Across the ring, Rea - in opposing blue - was marked up early, significant bruising forming under his orbital area as the fighters exchanged punishing blows.
The challenger, twenty-seven, landed power punches but the champion, 34, responded in kind with stinging uppercuts as the pace rarely dropped over twelve rounds.
The victor barely secured the result with official scores of draw, 115-113 and wider gap, but both fighters were relentless and courageous, everything their inspiration the legend embodied.
