UK light heavyweight Buatsi secured a victory yet unimpressive beginning to life under fresh promotional backing with a unanimous decision over Zach Parker in Manchester.
The Olympic bronze medallist's punch output appeared to earn him a judges' verdict in a competitive ten-round contest at the Co-op Live Arena.
But the challenger found success, delivering effective single shots in a contest where the approaches failed to mesh, with constant grabbing disrupting the fight.
The officials scored it 96-94 to Buatsi, with the third a 95-95.
"It wasn't my best performance but what defines champions? They succeed," the victor stated in the ringside as he was greeted with disapproval from the spectators.
The Londoner returned to winning ways after his maiden career setback - an epic battle with his previous opponent in February - to claim a 20th pro success.
Several boxing experts thought the challenger, 31, merited the decision but the British boxer suffered the second loss of his 28-match professional journey.
Buatsi Secures Triumph in Slow Affair
Buatsi's progress has plateaued in recent years through contract problems and considerable time of lack of fights.
Previously predicted as the next star of the British fight scene, he now is positioned trying to realize his potential - maybe in what feels like a ultimate opportunity - under fresh management.
He began cautiously, with both competitors ready to be aggressive in a tentative initial rounds.
The challenger, whose only previous defeat came at super-middleweight against John Ryder in 2022 after breaking his hand in the contest, was competing in only his second appearance at light heavyweight.
By the halfway stage, Parker had stayed in contention, causing problems for Buatsi, who worked behind a protective stance to barely take the better periods.
The crowd's patience decreased during regular grabbing, with Parker falling to the floor several times during clinches.
The underdog finished the stronger, but many rounds were difficult to score. Although, former world champion the boxing analyst - working with Dazn - had it strongly leaning for Parker, awarding Buatsi just one round.
Buatsi progresses, but with the likes of hard hitter David Benavidez, and Eastern European fighter Dmitry Bivol ruling the division, the path to championship success - based on this performance - still looks steep.
Ricky Hatton Memorial Fuels Manchester Derby Battle
In the supporting bout, Arthur overcame Rea by close verdict in a excellent all-Manchester fight to win the European light heavyweight championship.
The stadium grew hushed for a extremely emotional memorial ahead of the contest as ten bells rang in memory of the city's native Hatton, who died at age 46 in last month.
It was the premier televised match card in the urban center since the passing of Hatton. As the final chime faded, the quiet became a shout of "only one Ricky Hatton".
The fighting inside the ropes matched the feeling. The eventual winner was sent to the canvas by a significant blow flush on the face in the early round, rising shakily to his feet on the count of eight.
But the Manchester United-red equipment of Arthur soon came forward again. Across the ring, Rea - in opposing blue - was injured early, noticeable damage appearing under his orbital area as the pair traded punishing blows.
The challenger, twenty-seven, connected with strong blows but the champion, 34, responded in kind with powerful upward punches as the intensity rarely dropped over twelve rounds.
The victor narrowly won the result with judges scorecards of draw, close margin and clearer margin, but both fighters were persistent and courageous, all the qualities their hero the legend represented.
