UK light-heavyweight Buatsi made a winning yet unimpressive debut to life under fresh promotional backing with a points victory over Zach Parker in Manchester.
The Olympic bronze medallist's punch output appeared to earn him a majority decision in a close 10-round bout at the Manchester venue.
But Parker landed significant shots, landing some telling single shots in a fight where the styles didn't complement each other, with constant grabbing marring the fight.
The scoring judges had it 96-94 for to the winner, with the final judge a even score.
"It wasn't my greatest performance but what defines champions? They prevail," the victor said in the ring as he was faced disapproval from the crowd.
The British fighter got back to winning after his first professional defeat - an memorable fight with Callum Smith in February - to secure a 20th pro success.
Some ringside observers thought the challenger, 31, should have been awarded the victory but the Derbyshire fighter endured the second defeat of his 28-match career.
The Champion Claims Victory in Uneventful Encounter
The fighter's advancement has slowed in the past few years through promotional disputes and long spells of inactivity.
Previously predicted as the future of UK boxing, he now finds himself trying to fulfil that early promise - maybe in what appears to be a last chance - under recent support.
He started carefully, with the two boxers ready to be aggressive in a calculated early stages.
Parker, whose sole prior loss came at super-middleweight against John Ryder in 2022 after suffering a hand injury in the contest, was making just his second appearance at the higher weight class.
By the halfway stage, Parker had stayed in contention, making life awkward for Buatsi, who operated with a protective stance to edge the more effective stanzas.
The spectators' acceptance diminished because of regular grabbing, with Parker slipping to the canvas multiple occasions during clinches.
The underdog closed well, but multiple periods were difficult to score. However, previous titleholder Carl Frampton - commentating on Dazn - had it strongly leaning for Parker, awarding Buatsi just only one stanza.
Buatsi progresses, but with the caliber of hard hitter David Benavidez, and Russian champion Dmitry Bivol ruling the division, the journey to titles - based on this performance - still looks steep.
Hatton Memorial Fuels Manchester Derby Battle
In the supporting bout, Arthur overcame Rea by split-decision in a excellent Manchester vs Manchester battle to secure the European light-heavyweight belt.
The arena grew hushed for a profoundly moving memorial prior to the bout as 10 bells tolled in memory of the city's native Hatton, who passed away 46 years old in September.
It was the premier televised fight night in the location since Hatton's death. As the last bell disappeared, the silence gave way to a chant of "there's just one Ricky Hatton".
The action within the ring matched the sentiment. Arthur was sent to the canvas by a significant blow directly to the jaw in the initial stage, getting up unsteadily to his footing on the eight count.
But the traditional red attire of the fighter soon pressed ahead again. Across the ring, the opponent - in competitive blue - was marked up early, heavy swelling appearing under his face as the duo landed hard punches.
Rea, twenty-seven, delivered effective strikes but the champion, thirty-four, responded in kind with effective uppercuts as the pace seldom decreased over 12 rounds.
Arthur barely secured the verdict with official scores of draw, 115-113 and wider gap, but each competitor were determined and brave, everything their idol Hatton embodied.
