UK light-heavyweight Buatsi secured a victory yet underwhelming beginning to his career under fresh promotional backing with a unanimous decision over Zach Parker in Manchester.
The Olympic medal winner's punch output appeared to earn him a split decision in a competitive 10-round bout at the Co-op Live Arena.
But Parker had his moments, delivering effective single shots in a contest where the approaches didn't complement each other, with excessive holding spoiling the fight.
The scoring judges judged it 96-94 to the winner, with the remaining official a 95-95 draw.
"It wasn't my greatest display but what do champions do? They win," the victor commented in the arena as he was faced negative reactions from the crowd.
The British fighter returned to winning ways after his initial pro loss - an memorable fight with his previous opponent in February - to claim a 20th pro success.
Various analysts felt Parker, 31, deserved the win but the Derbyshire fighter endured the second defeat of his 28-match career.
The Champion Secures Triumph in Slow Affair
His career development has stalled in recent years through management issues and extended periods of lack of fights.
Earlier forecast as the future of UK boxing, he now stands trying to fulfil that early promise - maybe in what feels like a last chance - under fresh management.
He began cautiously, with the two boxers ready to be aggressive in a cagey opening few rounds.
Parker, whose single earlier setback came at super-middleweight against his former opponent in 2022 after breaking his hand mid-fight, was making just his second fight at the higher weight class.
By the fight's midpoint, Parker had made it competitive, causing problems for Buatsi, who utilized a tight guard to edge the more effective periods.
The spectators' acceptance decreased because of regular grabbing, with the challenger slipping to the canvas various instances during clinches.
The underdog closed well, but multiple periods were challenging to assess. However, ex-champion the boxing analyst - working with Dazn - had it strongly leaning for Parker, awarding Buatsi just only one stanza.
Buatsi advances, but with the caliber of power puncher David Benavidez, and Russian star Dmitry Bivol ruling the division, the road to world glory - judging by this showing - still looks steep.
Hatton Memorial Motivates Local Rivalry Fight
In the co-main event, Lyndon Arthur beat Rea by split-decision in a outstanding all-Manchester fight to capture the continental title.
The stadium grew hushed for a deeply poignant tribute prior to the bout as 10 bells tolled in remembrance of local hero Ricky Hatton, who succumbed aged 46 in September.
It was the premier televised fight night in the city since Hatton's passing. As the last bell faded, the stillness gave way to a roar of "there's only one Hatton".
The action within the ring reflected the emotion. The eventual winner was knocked down by a left hook squarely on the chin in the initial stage, getting up unsteadily to his feet on the eight count.
But the traditional red shorts of Arthur soon pressed ahead again. On the opposite side, Rea - in rival City blue - was injured quickly, noticeable damage appearing under his orbital area as the pair traded powerful shots.
Rea, twenty-seven, delivered effective strikes but Arthur, thirty-four, responded in kind with effective uppercuts as the action hardly diminished over twelve rounds.
The victor narrowly won the verdict with official scores of draw, close margin and clearer margin, but both fighters were relentless and courageous, all the qualities their inspiration Hatton embodied.
