UK light heavyweight Buatsi secured a victory yet unimpressive start to his career under new promoters with a points victory over Zach Parker in Manchester.
The Olympic bronze medallist's punch output appeared to earn him a majority decision in a competitive 10-round bout at the Co-op Live Arena.
But Parker had his moments, landing some telling clean blows in a fight where the techniques never quite clicked, with excessive holding disrupting the fight.
Two judges judged it 96-94 to the winner, with the third a 95-95.
"It wasn't my best showing but what do champions do? They succeed," the victor commented in the ringside as he was greeted with boos from the audience.
The British fighter got back to winning after his first professional defeat - an epic battle with his previous opponent in last winter - to secure a 20th pro success.
Several boxing experts believed Parker, 31, merited the win but the Derbyshire fighter suffered the second setback of his 28-match professional journey.
Buatsi Secures Win in Slow Affair
Buatsi's progress has plateaued in the past few years through contract problems and extended periods of inactivity.
Previously predicted as the future of British boxing, he now stands trying to realize his potential - maybe in what seems like a ultimate opportunity - under new promotional backing.
He opened tentatively, with the two boxers willing to take risks in a calculated initial rounds.
The challenger, whose single earlier setback came at the lower weight class against his former opponent in two years ago after suffering a hand injury during the bout, was competing in only his second bout at the higher weight class.
By the fight's midpoint, Parker had kept it close, causing problems for Buatsi, who worked behind a protective stance to narrowly win the more effective periods.
The spectators' acceptance diminished amid regular grabbing, with the challenger falling to the floor various instances during grappling.
Parker ended stronger, but multiple periods were hard to judge. Nevertheless, ex-champion the boxing analyst - working with the broadcast network - had it strongly leaning for Parker, awarding Buatsi just one round.
Buatsi advances, but with the likes of hard hitter David Benavidez, and Russian star Bivol leading the category, the journey to titles - based on this performance - still appears challenging.
Ricky Hatton Tribute Motivates Local Rivalry Battle
In the secondary fight, Lyndon Arthur overcame Rea by split-decision in a excellent Manchester vs Manchester fight to capture the European light heavyweight championship.
The venue grew hushed for a deeply poignant memorial ahead of the contest as 10 bells sounded in memory of the city's native Hatton, who passed away aged 46 in recently.
It was the initial significant broadcast match card in the city since Hatton's passing. As the last bell ended, the silence became a roar of "there's only one Ricky Hatton".
The competition within the ring matched the emotion. Arthur was floored by a significant blow directly to the chin in the second round, rising shakily to his footing on the referee's count.
But the traditional red equipment of the fighter soon advanced again. From the other corner, Rea - in rival City blue - was damaged early, heavy swelling developing under his eye as the duo exchanged punishing blows.
The challenger, twenty-seven, connected with strong blows but the champion, thirty-four, fought fire with fire with effective uppercuts as the action rarely dropped over twelve rounds.
Arthur narrowly won the decision with official scores of draw, 115-113 and clearer margin, but the two athletes were persistent and full of heart, everything their inspiration the legend embodied.
