UK light-heavyweight Buatsi made a winning yet unimpressive beginning to his career under fresh promotional backing with a points victory over Zach Parker in the Manchester arena.
The Olympic medal winner's activity level appeared to earn him a majority decision in a tight ten-round bout at the Manchester venue.
But the challenger found success, connecting with powerful clean blows in a match where the styles didn't complement each other, with constant grabbing marring the action.
Two judges scored it 96-94 in favor to Buatsi, with the remaining official a 95-95.
"It wasn't my best showing but how do champions respond? They succeed," Buatsi said in the ringside as he was faced disapproval from the audience.
The British fighter returned to winning ways after his initial pro loss - an thrilling contest with Callum Smith in last winter - to claim a 20th career victory.
Various analysts thought the challenger, 31, deserved the decision but the contender experienced the second defeat of his 28-fight career.
Buatsi Secures Triumph in Uneventful Match
Buatsi's progress has slowed in recent times through contract problems and considerable time of inactivity.
Previously predicted as the future of British boxing, he now stands trying to fulfil that early promise - maybe in what appears to be a last chance - under fresh management.
He began cautiously, with neither fighter ready to take risks in a calculated initial rounds.
The challenger, whose single earlier setback came at the lower weight class against his former opponent in 2022 after breaking his hand mid-fight, was competing in only his second appearance at the higher weight class.
By the middle rounds, Parker had stayed in contention, causing problems for Buatsi, who utilized a solid defense to narrowly win the more effective stanzas.
The crowd's patience decreased during constant clinching, with Parker slipping to the canvas various instances during close exchanges.
Parker ended stronger, but many rounds were difficult to score. However, ex-champion the boxing analyst - commentating on Dazn - had it strongly leaning for the challenger, giving Buatsi just only one stanza.
The victor moves on, but with the caliber of heavy hitter David Benavidez, and Eastern European fighter Bivol ruling the division, the path to championship success - based on this performance - still appears challenging.
Ricky Hatton Tribute Fuels Manchester Derby Fight
In the co-main event, Lyndon Arthur beat Rea by close verdict in a outstanding local rivalry battle to secure the continental title.
The arena grew hushed for a profoundly moving tribute before the fight as ten bells rang in remembrance of Manchester's own Hatton, who passed away aged 46 in September.
It was the first major televised fight night in the location since the passing of Hatton. As the last bell faded, the silence transitioned to a roar of "there's only one Ricky Hatton".
The competition inside the ropes equaled the sentiment. The eventual winner was sent to the canvas by a powerful punch directly to the face in the early round, rising shakily to his feet on the referee's count.
But the Manchester United-red equipment of Arthur soon came forward again. Across the ring, Rea - in opposing blue - was marked up soon, noticeable damage forming under his eye as the fighters landed powerful shots.
Rea, twenty-seven, landed power punches but the champion, thirty-four, fought fire with fire with powerful upward punches as the pace seldom decreased over 12 rounds.
The victor barely secured the decision with scoring tallies of 114-114, narrow lead and wider gap, but both fighters were relentless and courageous, everything their idol the legend embodied.
