UK light heavyweight Buatsi made a winning yet underwhelming beginning to his career under fresh promotional backing with a points victory over Zach Parker in Manchester.
The Olympic bronze medallist's punch output appeared to earn him a split decision in a close 10-round contest at the Co-op Live Arena.
But the challenger had his moments, connecting with powerful clean blows in a contest where the approaches failed to mesh, with excessive holding disrupting the contest.
The scoring judges judged it 96-94 for to the winner, with the final judge a even score.
"It wasn't my best performance but what do champions do? They win," Buatsi said in the arena as he was faced boos from the spectators.
The British fighter got back to winning after his maiden career setback - an thrilling contest with Callum Smith in last winter - to secure a 20th pro success.
Some ringside observers believed Parker, thirty-one, merited the win but the British boxer experienced the second loss of his 28-fight professional journey.
Buatsi Earns Victory in Slow Encounter
Buatsi's progress has plateaued in the past few years through management issues and considerable time of inactivity.
Earlier forecast as the future of UK boxing, he now stands trying to achieve expectations - maybe in what feels like a ultimate opportunity - under recent support.
He started carefully, with neither fighter ready to be aggressive in a calculated early stages.
Parker, whose single earlier setback came at the lower weight class against his former opponent in two years ago after breaking his hand mid-fight, was participating in his second bout at light-heavyweight.
By the halfway stage, the underdog had made it competitive, making life awkward for Buatsi, who utilized a solid defense to edge the cleaner rounds.
The spectators' acceptance decreased during regular grabbing, with Parker going down various instances during grappling.
Parker finished the stronger, but several stanzas were difficult to score. However, previous titleholder the boxing analyst - commentating on Dazn - had it significantly in favor for Parker, awarding Buatsi just one round.
Buatsi advances, but with the presence of power puncher David Benavidez, and Russian champion Bivol dominating the weight class, the journey to titles - based on this performance - still appears challenging.
Hatton Tribute Fuels Local Rivalry Battle
In the secondary fight, Lyndon Arthur overcame Rea by split-decision in a terrific Manchester vs Manchester battle to capture the European light heavyweight championship.
The stadium became quiet for a extremely emotional tribute prior to the bout as ten bells sounded in memory of Manchester's own Ricky Hatton, who succumbed 46 years old in last month.
It was the initial significant broadcast fight night in the location since Hatton's death. As the final chime faded, the quiet transitioned to a roar of "there's only one Hatton".
The fighting during the bout reflected the feeling. Arthur was sent to the canvas by a significant blow directly to the face in the early round, standing uncertainly to his position on the referee's count.
But the red-colored attire of the fighter soon advanced again. From the other corner, the opponent - in opposing blue - was injured early, noticeable damage developing under his orbital area as the pair traded powerful shots.
Rea, 27, landed power punches but Arthur, thirty-four, fought fire with fire with stinging uppercuts as the intensity rarely dropped over 12 rounds.
Arthur barely secured the result with judges scorecards of 114-114, narrow lead and clearer margin, but both fighters were relentless and brave, exactly what their inspiration Hatton embodied.
