British light-heavyweight Buatsi made a winning yet underwhelming debut to his career under recent management with a decision win over Zach Parker in Manchester.
The Olympic bronze medallist's activity level likely gained him a split decision in a close ten-round fight at the Co-op Live Arena.
But Parker landed significant shots, delivering effective single shots in a match where the approaches failed to mesh, with constant grabbing marring the action.
Two judges had it 96-94 to the winner, with the final judge a 95-95 draw.
"It wasn't my finest performance but what do champions do? They win," Buatsi stated in the ringside as he was faced negative reactions from the spectators.
The British fighter bounced back after his maiden career setback - an thrilling contest with Callum Smith in February - to secure a twentieth professional win.
Some ringside observers felt Parker, 31, merited the victory but the Derbyshire fighter endured the second defeat of his 28-match professional journey.
The Champion Secures Victory in Uneventful Encounter
Buatsi's progress has plateaued in recent years through management issues and extended periods of lack of fights.
Earlier forecast as the rising talent of British boxing, he now is positioned trying to fulfil that early promise - possibly in what feels like a final roll of the dice - under fresh management.
He started carefully, with both competitors prepared to overcommit in a calculated opening few rounds.
The challenger, whose single earlier setback came at super-middleweight against John Ryder in 2022 after suffering a hand injury during the bout, was participating in his second fight at light-heavyweight.
By the fight's midpoint, Parker had stayed in contention, making life awkward for the favorite, who utilized a protective stance to narrowly win the cleaner rounds.
The audience's tolerance decreased amid regular grabbing, with Parker going down various instances during grappling.
The underdog ended stronger, but several stanzas were difficult to score. Nevertheless, previous titleholder the boxing analyst - commentating on Dazn - had it strongly leaning for Parker, awarding Buatsi just one round.
The victor advances, but with the caliber of power puncher David Benavidez, and Russian champion Bivol leading the category, the path to championship success - judging by this showing - still appears challenging.
Hatton Memorial Fuels Local Rivalry Contest
In the supporting bout, Lyndon Arthur defeated Bradley Rea by split-decision in a terrific local rivalry fight to win the continental belt.
The arena grew hushed for a deeply poignant memorial before the fight as a bell ceremony rang in remembrance of local hero Hatton, who died at age 46 in September.
It was the initial significant broadcast match card in the urban center since Hatton's passing. As the last bell faded, the quiet became a shout of "there's only one Ricky Hatton".
The competition within the ring matched the feeling. Arthur was floored by a powerful punch directly to the jaw in the initial stage, standing uncertainly to his footing on the eight count.
But the Manchester United-red shorts of Arthur soon came forward again. Across the ring, Rea - in rival City blue - was damaged soon, heavy swelling forming under his eye as the pair exchanged hard punches.
The challenger, 27, landed power punches but the champion, 34, matched the intensity with stinging uppercuts as the pace hardly diminished over twelve rounds.
The victor barely secured the verdict with judges scorecards of 114-114, 115-113 and 115-112, but both fighters were persistent and brave, exactly what their idol Hatton embodied.
