British light heavyweight Buatsi earned a win yet underwhelming start to life under recent management with a unanimous decision over Zach Parker in Manchester.
The Olympic medal winner's punch output likely gained him a judges' verdict in a close 10-round fight at the Co-op Live Arena.
But the challenger found success, delivering effective individual punches in a match where the styles didn't complement each other, with constant grabbing spoiling the contest.
The officials judged it 96-94 for to the winner, with the third a 95-95 draw.
"It wasn't my finest showing but how do champions respond? They win," the victor said in the ringside as he was faced boos from the crowd.
The Londoner got back to winning after his maiden career setback - an epic battle with his previous opponent in last winter - to claim a twentieth professional win.
Some ringside observers felt the challenger, 31, merited the decision but the contender suffered the second loss of his 28-bout professional journey.
The Champion Secures Victory in Slow Match
Buatsi's progress has stalled in the past few years through promotional disputes and considerable time of inactivity.
Previously predicted as the rising talent of the British fight scene, he now stands trying to achieve expectations - maybe in what seems like a last chance - under recent support.
He opened tentatively, with the two boxers prepared to take risks in a cagey opening few rounds.
Parker, whose sole prior loss came at super-middleweight against his former opponent in two years ago after breaking his hand during the bout, was competing in only his second appearance at the higher weight class.
By the fight's midpoint, Parker had made it competitive, creating difficulties for the favorite, who utilized a solid defense to narrowly win the better rounds.
The crowd's patience wore thin during frequent holding, with Parker slipping to the canvas various instances during close exchanges.
The underdog finished the stronger, but many rounds were difficult to score. However, ex-champion the boxing analyst - working with Dazn - had it strongly leaning for Parker, giving Buatsi just only one stanza.
Buatsi progresses, but with the presence of heavy hitter David Benavidez, and Russian star Bivol dominating the weight class, the road to world glory - on this evidence - still looks steep.
Ricky Hatton Memorial Motivates All-Manchester Fight
In the supporting bout, Lyndon Arthur defeated Bradley Rea by close verdict in a terrific local rivalry contest to secure the continental championship.
The venue grew hushed for a profoundly moving memorial before the fight as 10 bells sounded in memory of local hero Ricky Hatton, who died aged 46 in September.
It was the premier televised match card in the location since the passing of Hatton. As the concluding sound disappeared, the silence became a chant of "there's just one Ricky Hatton".
The action within the ring reflected the feeling. Arthur was knocked down by a powerful punch squarely on the face in the initial stage, rising shakily to his footing on the referee's count.
But the Manchester United-red equipment of the fighter soon advanced again. From the other corner, Rea - in opposing blue - was injured early, significant bruising forming under his face as the fighters traded hard punches.
The challenger, twenty-seven, landed power punches but Arthur, 34, responded in kind with stinging uppercuts as the pace seldom decreased over twelve rounds.
Arthur edged the decision with judges scorecards of 114-114, close margin and wider gap, but both fighters were relentless and courageous, everything their inspiration the legend stood for.
