UK light heavyweight Buatsi made a winning yet disappointing beginning to life under new promoters with a unanimous decision over Zach Parker in Manchester.
The Olympic bronze medallist's punch output appeared to earn him a majority decision in a competitive 10-round fight at the Manchester venue.
But Parker found success, landing some telling single shots in a contest where the styles didn't complement each other, with constant grabbing spoiling the action.
Two judges had it 96-94 in favor to the winner, with the remaining official a even score.
"It wasn't my best display but what do champions do? They succeed," the victor stated in the ringside as he was faced boos from the crowd.
The Londoner returned to winning ways after his initial pro loss - an thrilling contest with Callum Smith in last winter - to secure a twentieth professional win.
Some ringside observers felt the challenger, thirty-one, merited the win but the Derbyshire fighter endured the second defeat of his 28-match professional journey.
Buatsi Secures Triumph in Dull Encounter
The fighter's advancement has plateaued in recent years through promotional disputes and extended periods of inactivity.
Previously predicted as the rising talent of the British fight scene, he now stands trying to realize his potential - possibly in what feels like a last chance - under new promotional backing.
He opened tentatively, with the two boxers prepared 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 breaking his hand mid-fight, was competing in only his second fight at light-heavyweight.
By the fight's midpoint, the underdog had stayed in contention, creating difficulties for Buatsi, who utilized a solid defense to edge the more effective stanzas.
The audience's tolerance diminished amid frequent holding, with the challenger falling to the floor multiple occasions during close exchanges.
The underdog finished the stronger, but many rounds were difficult to score. Although, previous titleholder the boxing analyst - commentating on the broadcast network - had it particularly wide for the challenger, scoring for Buatsi just a single round.
Buatsi advances, but with the presence of hard hitter David Benavidez, and Eastern European fighter Dmitry Bivol leading the category, the path to championship success - judging by this showing - still seems difficult.
Hatton Tribute Inspires Manchester Derby Battle
In the co-main event, Lyndon Arthur beat Rea by divided decision in a terrific all-Manchester battle to secure the continental championship.
The stadium grew hushed for a deeply poignant homage ahead of the contest as a bell ceremony sounded in remembrance of Manchester's own Ricky Hatton, who died aged 46 in recently.
It was the premier televised match card in the city since the passing of Hatton. As the last bell faded, the silence gave way to a chant of "there's just one Ricky Hatton".
The competition during the bout reflected the feeling. The eventual winner was knocked down by a left hook squarely on the chin in the second round, getting up unsteadily to his footing on the count of eight.
But the Manchester United-red equipment of the fighter soon pressed ahead again. On the opposite side, the opponent - in rival City blue - was injured soon, significant bruising developing under his orbital area as the fighters landed punishing blows.
Rea, twenty-seven, delivered effective strikes but Arthur, thirty-four, matched the intensity with powerful upward punches as the intensity rarely dropped over 12 rounds.
Arthur barely secured the decision with scoring tallies of draw, narrow lead and clearer margin, but the two athletes were determined and full of heart, exactly what their hero Hatton stood for.
