British light-heavyweight Buatsi secured a victory yet unimpressive beginning to his career under new promoters with a points victory over Zach Parker in Manchester.
The Olympic bronze medallist's punch output likely gained him a judges' verdict in a tight ten-round bout at the Manchester venue.
But the challenger landed significant shots, landing some telling clean blows in a contest where the approaches didn't complement each other, with excessive holding disrupting the contest.
The scoring judges scored it 96-94 to the winner, with the final judge a 95-95.
"It wasn't my greatest performance but what do champions do? They succeed," the victor stated in the ring as he was greeted with negative reactions from the crowd.
The Londoner bounced back after his maiden career setback - an epic battle with his previous opponent in February - to earn a 20th pro success.
Several boxing experts thought the challenger, thirty-one, should have been awarded the win but the British boxer experienced the second defeat of his 28-match professional journey.
Buatsi Secures Triumph in Slow Encounter
Buatsi's progress has plateaued in the past few years through contract problems and considerable time of inactivity.
Once tipped as the future of the British fight scene, he now stands trying to fulfil that early promise - possibly in what appears to be a ultimate opportunity - under recent support.
He started carefully, with both competitors prepared to be aggressive in a tentative initial rounds.
The challenger, whose only previous defeat came at super middleweight against his former opponent in two years ago after breaking his hand mid-fight, was competing in only his second fight at the higher weight class.
By the fight's midpoint, the underdog had kept it close, causing problems for the favorite, who operated with a solid defense to edge the cleaner periods.
The audience's tolerance decreased during frequent holding, with Parker going down multiple occasions during grappling.
Parker finished the stronger, but multiple periods were hard to judge. Although, previous titleholder Carl Frampton - providing analysis for Dazn - had it strongly leaning for Parker, scoring for Buatsi just one round.
The victor moves on, but with the likes of hard hitter David Benavidez, and Russian champion Dmitry Bivol dominating the weight class, the journey to titles - on this evidence - still appears challenging.
Ricky Hatton Homage Inspires Local Rivalry Fight
In the co-main event, Lyndon Arthur defeated Rea by close verdict in a outstanding local rivalry battle to capture the continental belt.
The venue fell silent for a extremely emotional memorial before the fight as ten bells sounded in memory of local hero Hatton, who died aged 46 in last month.
It was the initial significant broadcast fight night in the city since Hatton's death. As the last bell ended, the stillness became a roar of "there's just one Ricky Hatton".
The fighting within the ring equaled the feeling. Arthur was floored by a powerful punch directly to the chin in the second round, standing uncertainly to his feet on the count of eight.
But the red-colored equipment of the fighter soon came forward again. On the opposite side, the opponent - in opposing blue - was marked up quickly, noticeable damage developing under his face as the pair exchanged punishing blows.
Rea, twenty-seven, landed power punches but Arthur, thirty-four, fought fire with fire with stinging uppercuts as the action hardly diminished over 12 rounds.
Arthur narrowly won the verdict with judges scorecards of 114-114, 115-113 and wider gap, but the two athletes were relentless and brave, everything their inspiration Hatton embodied.
