UK light heavyweight Buatsi made a winning yet underwhelming beginning to his career under new promoters with a decision win over Zach Parker in Manchester.
The Olympic medal winner's activity level appeared to earn him a judges' verdict in a competitive 10-round bout at the Co-op Live Arena.
But Parker landed significant shots, landing some telling individual punches in a fight where the styles never quite clicked, with excessive holding marring the contest.
Two judges judged it 96-94 for to the winner, with the final judge a 95-95.
"It wasn't my best display but what do champions do? They succeed," Buatsi commented in the ring as he was met by boos from the spectators.
The Londoner returned to winning ways after his first professional defeat - an memorable fight with Callum Smith in last winter - to secure a twentieth professional win.
Some ringside observers thought the challenger, thirty-one, deserved the victory but the Derbyshire fighter experienced the second defeat of his 28-bout career.
The Champion Secures Win in Dull Affair
The fighter's advancement has slowed in the past few years through management issues and considerable time of inactivity.
Previously predicted as the future of UK boxing, he now finds himself trying to fulfil that early promise - possibly in what seems like a last chance - under new promotional backing.
He began cautiously, with neither fighter willing to take risks in a cagey early stages.
Parker, whose single earlier setback came at super-middleweight against John Ryder in two years ago after suffering a hand injury mid-fight, was competing in only his second appearance at the higher weight class.
By the middle rounds, Parker had kept it close, causing problems for the favorite, who operated with a tight guard to narrowly win the cleaner rounds.
The crowd's patience decreased amid constant clinching, with Parker going down multiple occasions during close exchanges.
The underdog finished the stronger, but many rounds were challenging to assess. Nevertheless, former world champion the boxing analyst - providing analysis for Dazn - had it strongly leaning for the challenger, awarding Buatsi just only one stanza.
The victor progresses, but with the caliber of heavy hitter David Benavidez, and Russian champion Bivol leading the category, the journey to titles - judging by this showing - still appears challenging.
Hatton Homage Fuels Local Rivalry Battle
In the co-main event, Lyndon Arthur beat Rea by split-decision in a outstanding all-Manchester battle to win the European light-heavyweight title.
The stadium fell silent for a extremely emotional homage prior to the bout as a bell ceremony rang in memory of local hero Hatton, who passed away 46 years old in last month.
It was the first major televised fight night in the location since Hatton's death. As the last bell ended, the stillness became a roar of "only one Hatton".
The fighting within the ring reflected the feeling. The eventual winner was knocked down by a significant blow directly to the chin in the second round, standing uncertainly to his footing on the count of eight.
But the traditional red equipment of Arthur soon advanced again. On the opposite side, the opponent - in competitive blue - was damaged quickly, heavy swelling developing under his eye as the pair landed punishing blows.
The challenger, 27, delivered effective strikes but Arthur, thirty-four, matched the intensity with powerful upward punches as the pace seldom decreased over the full distance.
The victor barely secured the decision with scoring tallies of even score, 115-113 and wider gap, but the two athletes were determined and brave, everything their inspiration the legend stood for.
