British light heavyweight Buatsi earned a win yet underwhelming debut to his career under fresh promotional backing with a unanimous decision over Zach Parker in Manchester.
The Olympic bronze medallist's punch output likely gained him a majority decision in a close ten-round bout at the Manchester venue.
But the challenger found success, connecting with powerful clean blows in a contest where the approaches didn't complement each other, with excessive holding marring the action.
Two judges judged it 96-94 for to the winner, with the remaining official a even score.
"It wasn't my best performance but how do champions respond? They prevail," the victor commented in the ring as he was greeted with boos from the crowd.
The British fighter bounced back after his initial pro loss - an epic battle with his previous opponent in February - to earn a twentieth professional win.
Some ringside observers believed the challenger, 31, merited the victory but the contender suffered the second setback of his 28-bout career.
Buatsi Claims Win in Dull Encounter
The fighter's advancement has plateaued in recent years through contract problems and considerable time of inactivity.
Once tipped as the future of the British fight scene, he now is positioned trying to fulfil that early promise - perhaps in what feels like a final roll of the dice - under new promotional backing.
He opened tentatively, with neither fighter ready to overcommit in a cagey initial rounds.
Parker, whose only previous defeat came at super-middleweight against his former opponent in two years ago after damaging his hand mid-fight, was competing in only his second fight at the higher weight class.
By the fight's midpoint, Parker had made it competitive, creating difficulties for Buatsi, who worked behind a protective stance to narrowly win the better periods.
The spectators' acceptance diminished amid regular grabbing, with the challenger slipping to the canvas several times during close exchanges.
Parker ended stronger, but many rounds were difficult to score. Nevertheless, former world champion Carl Frampton - commentating on Dazn - had it strongly leaning for Parker, giving Buatsi just a single round.
Buatsi moves on, but with the likes of hard hitter David Benavidez, and Russian champion Dmitry Bivol dominating the weight class, the path to championship success - judging by this showing - still appears challenging.
Ricky Hatton Homage Inspires Manchester Derby Fight
In the supporting bout, Lyndon Arthur overcame Rea by divided decision in a outstanding Manchester vs Manchester fight to capture the European light-heavyweight belt.
The venue fell silent for a deeply poignant memorial prior to the bout as a bell ceremony rang in remembrance of the city's native Ricky Hatton, who passed away aged 46 in last month.
It was the initial significant broadcast fight night in the city since Hatton's death. As the final chime disappeared, the quiet transitioned to a roar of "there's only one Hatton".
The fighting inside the ropes reflected the emotion. Arthur was floored by a significant blow squarely on the jaw in the initial stage, standing uncertainly to his feet on the referee's count.
But the Manchester United-red shorts of the fighter soon pressed ahead again. From the other corner, the opponent - in competitive blue - was injured soon, noticeable damage appearing under his orbital area as the fighters landed punishing blows.
The challenger, twenty-seven, landed power punches but the champion, thirty-four, matched the intensity with effective uppercuts as the pace seldom decreased over the full distance.
The victor narrowly won the result with official scores of 114-114, narrow lead and clearer margin, but both fighters were relentless and full of heart, everything their inspiration the legend represented.
