British light-heavyweight Buatsi made a winning yet underwhelming beginning to his career under fresh promotional backing with a decision win over Zach Parker in Manchester.
The Olympic bronze medallist's work rate appeared to earn him a majority decision in a close ten-round bout at the Manchester venue.
But the challenger landed significant shots, delivering effective clean blows in a contest where the techniques failed to mesh, with constant grabbing marring the contest.
The scoring judges scored it 96-94 in favor to the winner, with the third a 95-95 draw.
"It wasn't my finest display but what do champions do? They prevail," the victor said in the arena as he was faced negative reactions from the crowd.
The Londoner bounced back after his initial pro loss - an memorable fight with his previous opponent in February - to earn a twentieth professional win.
Various analysts thought the challenger, thirty-one, deserved the decision but the contender experienced the second setback of his 28-bout professional journey.
The Champion Secures Victory in Slow Affair
Buatsi's progress has plateaued in the past few years through contract problems and extended periods of lack of fights.
Once tipped as the future of British boxing, he now stands trying to fulfil that early promise - perhaps in what feels like a ultimate opportunity - under recent support.
He started carefully, with both competitors prepared to take risks in a tentative early stages.
The challenger, whose sole prior loss came at the lower weight class against John Ryder in 2022 after breaking his hand in the contest, was competing in only his second bout at light-heavyweight.
By the fight's midpoint, Parker had kept it close, making life awkward for the favorite, who operated with a protective stance to edge the more effective periods.
The audience's tolerance decreased amid frequent holding, with the challenger falling to the floor various instances during grappling.
The underdog ended stronger, but many rounds were hard to judge. Nevertheless, previous titleholder Carl Frampton - working with the broadcast network - had it particularly wide for Parker, scoring for Buatsi just one round.
Buatsi moves on, but with the likes of power puncher David Benavidez, and Russian champion Dmitry Bivol leading the category, the road to world glory - on this evidence - still looks steep.
Ricky Hatton Homage Motivates Manchester Derby Contest
In the supporting bout, Arthur overcame Rea by divided decision in a excellent local rivalry fight to capture the European light heavyweight championship.
The venue grew hushed for a profoundly moving homage ahead of the contest as a bell ceremony tolled in honor of Manchester's own Ricky Hatton, who died aged 46 in recently.
It was the initial significant broadcast boxing event in the urban center since Hatton's death. As the last bell disappeared, the silence transitioned to a chant of "there's only one Ricky Hatton".
The action inside the ropes equaled the feeling. Arthur was floored by a powerful punch flush on the jaw in the early round, getting up unsteadily to his footing on the eight count.
But the traditional red attire of the fighter soon came forward again. Across the ring, Rea - in opposing blue - was injured quickly, significant bruising appearing under his eye as the duo landed hard punches.
The challenger, 27, landed power punches but the champion, thirty-four, matched the intensity with stinging uppercuts as the action seldom decreased over the full distance.
The victor edged the result with scoring tallies of 114-114, narrow lead and wider gap, but both fighters were relentless and brave, everything their idol the legend represented.
