UK light heavyweight Buatsi earned a win yet disappointing beginning to life under fresh promotional backing with a points victory over Zach Parker in Manchester.
The Olympic medal winner's punch output likely gained him a split decision in a tight ten-round fight at the Co-op Live Arena.
But Parker had his moments, landing some telling single shots in a contest where the approaches didn't complement each other, with excessive holding spoiling the action.
Two judges judged it 96-94 in favor to Buatsi, with the remaining official a 95-95.
"It wasn't my best performance but what defines champions? They win," the victor commented in the ringside as he was faced disapproval from the spectators.
The Londoner returned to winning ways after his maiden career setback - an thrilling contest with his previous opponent in February - to claim a 20th pro success.
Some ringside observers thought the challenger, 31, deserved the win but the contender endured the second setback of his 28-match professional journey.
Buatsi Secures Victory in Slow Match
His career development has stalled in recent times through promotional disputes and considerable time of inactivity.
Once tipped as the future of UK boxing, he now finds himself trying to achieve expectations - perhaps in what feels like a final roll of the dice - under fresh management.
He opened tentatively, with both competitors ready to take risks in a calculated early stages.
Parker, whose only previous defeat came at super-middleweight against John Ryder in two years ago after damaging his hand mid-fight, was making just his second fight at the higher weight class.
By the halfway stage, the underdog had stayed in contention, creating difficulties for Buatsi, who utilized a solid defense to narrowly win the better rounds.
The audience's tolerance wore thin amid frequent holding, with Parker falling to the floor several times during close exchanges.
The underdog ended stronger, but many rounds were challenging to assess. Nevertheless, previous titleholder the boxing analyst - providing analysis for the broadcast network - had it significantly in favor for Parker, awarding Buatsi just only one stanza.
Buatsi moves on, but with the presence of power puncher David Benavidez, and Russian star Dmitry Bivol leading the category, the road to world glory - based on this performance - still looks steep.
Hatton Homage Motivates All-Manchester Battle
In the supporting bout, Lyndon Arthur beat Rea by close verdict in a excellent all-Manchester fight to secure the European light heavyweight championship.
The arena became quiet for a extremely emotional homage prior to the bout as a bell ceremony rang in honor of Manchester's own Ricky Hatton, who died aged 46 in recently.
It was the initial significant broadcast fight night in the city since Hatton's death. As the concluding sound ended, the stillness became a shout of "only one Ricky Hatton".
The action during the bout reflected the feeling. Arthur was knocked down by a significant blow directly to the face in the initial stage, standing uncertainly to his position on the eight count.
But the Manchester United-red shorts of Arthur soon pressed ahead again. From the other corner, Rea - in rival City blue - was injured early, noticeable damage developing under his orbital area as the duo exchanged powerful shots.
Rea, twenty-seven, delivered effective strikes but the champion, thirty-four, responded in kind with powerful upward punches as the intensity rarely dropped over 12 rounds.
The victor edged the verdict with scoring tallies of draw, narrow lead and clearer margin, but both fighters were determined and full of heart, exactly what their hero Hatton stood for.
