UK light-heavyweight Buatsi made a winning yet disappointing debut to his career under new promoters with a unanimous decision over Zach Parker in Manchester.
The Olympic medal winner's punch output seemingly secured him a split decision in a close 10-round contest at the Manchester venue.
But the challenger had his moments, landing some telling individual punches in a fight where the styles didn't complement each other, with constant grabbing disrupting the fight.
Two judges had it 96-94 for to Buatsi, with the remaining official a 95-95 draw.
"It wasn't my greatest showing but how do champions respond? They prevail," Buatsi said in the ringside as he was faced negative reactions from the spectators.
The British fighter got back to winning after his initial pro loss - an epic battle with his previous opponent in February - to secure a 20th pro success.
Several boxing experts believed the challenger, 31, merited the decision but the Derbyshire fighter suffered the second defeat of his 28-bout professional journey.
Buatsi Secures Victory in Uneventful Affair
The fighter's advancement has plateaued in recent years through management issues and considerable time of inactivity.
Previously predicted as the future of British boxing, he now is positioned trying to realize his potential - possibly in what appears to be a ultimate opportunity - under new promotional backing.
He started carefully, with neither fighter ready to overcommit in a calculated early stages.
The challenger, whose sole prior loss came at super middleweight against John Ryder in 2022 after damaging his hand in the contest, was competing in only his second fight at light heavyweight.
By the halfway stage, Parker had made it competitive, causing problems for the favorite, who worked behind a protective stance to narrowly win the better periods.
The audience's tolerance wore thin because of frequent holding, with Parker going down multiple occasions during clinches.
The underdog closed well, but many rounds were hard to judge. Nevertheless, ex-champion Carl Frampton - providing analysis for the broadcast network - had it strongly leaning for the challenger, giving Buatsi just a single round.
Buatsi moves on, but with the caliber of heavy hitter David Benavidez, and Russian star Dmitry Bivol leading the category, the road to world glory - on this evidence - still appears challenging.
Ricky Hatton Homage Fuels Local Rivalry Contest
In the co-main event, Lyndon Arthur overcame Rea by close verdict in a outstanding Manchester vs Manchester fight to capture the European light-heavyweight championship.
The venue grew hushed for a deeply poignant homage ahead of the contest as ten bells tolled in remembrance of local hero Ricky Hatton, who passed away aged 46 in September.
It was the premier televised match card in the city since Hatton's passing. As the final chime disappeared, the stillness became a chant of "only one Ricky Hatton".
The fighting inside the ropes matched the emotion. The eventual winner was knocked down by a powerful punch directly to the jaw in the second round, standing uncertainly to his position on the count of eight.
But the red-colored equipment of the fighter soon pressed ahead again. On the opposite side, the opponent - in rival City blue - was marked up soon, noticeable damage developing under his eye as the pair landed punishing blows.
Rea, twenty-seven, delivered effective strikes but the champion, 34, fought fire with fire with powerful upward punches as the pace rarely dropped over 12 rounds.
Arthur edged the verdict with judges scorecards of 114-114, 115-113 and wider gap, but each competitor were persistent and courageous, exactly what their idol Hatton represented.
