UK light heavyweight Buatsi made a winning yet underwhelming start to his career under recent management with a decision win over Zach Parker in Manchester.
The Olympic medal winner's punch output appeared to earn him a judges' verdict in a tight 10-round fight at the boxing arena.
But the challenger found success, landing some telling single shots in a match where the techniques didn't complement each other, with frequent clinching spoiling the contest.
The scoring judges judged it 96-94 in favor to the winner, with the final judge a 95-95.
"It wasn't my greatest showing but what defines champions? They win," Buatsi said in the ring as he was greeted with disapproval from the audience.
The Londoner returned to winning ways after his first professional defeat - an thrilling contest with Callum Smith in last winter - to secure a 20th career victory.
Several boxing experts believed Parker, thirty-one, merited the decision but the Derbyshire fighter endured the second defeat of his 28-match professional journey.
Buatsi Secures Triumph in Slow Encounter
His career development has plateaued in recent years through management issues and considerable time of lack of fights.
Previously predicted as the next star of the British fight scene, he now finds himself trying to realize his potential - perhaps in what seems like a final roll of the dice - under fresh management.
He opened tentatively, with both competitors ready to overcommit in a tentative opening few rounds.
The challenger, whose sole prior loss came at super-middleweight against John Ryder in two years ago after breaking his hand mid-fight, was competing in only his second fight at light-heavyweight.
By the halfway stage, the underdog had made it competitive, making life awkward for Buatsi, who utilized a tight guard to narrowly win the cleaner rounds.
The crowd's patience wore thin because of constant clinching, with Parker going down several times during grappling.
Parker ended stronger, but many rounds were challenging to assess. Although, previous titleholder the boxing analyst - working with Dazn - had it particularly wide for the challenger, giving Buatsi just one round.
Buatsi moves on, but with the presence of heavy hitter David Benavidez, and Russian star Bivol ruling the division, the journey to titles - based on this performance - still looks steep.
Ricky Hatton Tribute Motivates Manchester Derby Fight
In the supporting bout, Lyndon Arthur defeated Rea by split-decision in a terrific Manchester vs Manchester fight to secure the European light heavyweight belt.
The venue grew hushed for a deeply poignant tribute ahead of the contest as a bell ceremony sounded in memory of local hero Hatton, who passed away aged 46 in last month.
It was the first major televised boxing event in the location since Hatton's death. As the final chime faded, the stillness transitioned to a roar of "only one Hatton".
The action during the bout equaled the sentiment. The eventual winner was floored by a left hook flush on the jaw in the initial stage, standing uncertainly to his position on the referee's count.
But the traditional red equipment of Arthur soon advanced again. Across the ring, the opponent - in opposing blue - was damaged soon, significant bruising developing under his orbital area as the duo traded hard punches.
The challenger, twenty-seven, connected with strong blows but Arthur, thirty-four, fought fire with fire with powerful upward punches as the pace rarely dropped over the full distance.
Arthur edged the result with scoring tallies of even score, narrow lead and wider gap, but the two athletes were determined and courageous, all the qualities their hero the legend embodied.
