British light-heavyweight Buatsi made a winning yet disappointing beginning to life under fresh promotional backing with a decision win over Zach Parker in the Manchester arena.
The Olympic bronze medallist's activity level likely gained him a judges' verdict in a tight 10-round contest at the Co-op Live Arena.
But the challenger landed significant shots, landing some telling single shots in a contest where the techniques never quite clicked, with constant grabbing spoiling the contest.
The officials had it 96-94 to the winner, with the final judge a even score.
"It wasn't my best showing but how do champions respond? They win," Buatsi said in the arena as he was faced disapproval from the audience.
The British fighter got back to winning after his first professional defeat - an thrilling contest with his previous opponent in last winter - to secure a 20th pro success.
Several boxing experts believed the challenger, 31, merited the win but the Derbyshire fighter experienced the second defeat of his 28-match professional journey.
The Champion Earns Victory in Dull Match
The fighter's advancement has plateaued in recent years through contract problems and extended periods of inactivity.
Previously predicted as the rising talent of British boxing, he now stands trying to fulfil that early promise - possibly in what seems like a last chance - under recent support.
He opened tentatively, with the two boxers ready to be aggressive in a calculated initial rounds.
Parker, whose single earlier setback came at super middleweight against his former opponent in 2022 after damaging his hand in the contest, was making just his second appearance at light heavyweight.
By the fight's midpoint, Parker had kept it close, creating difficulties for the favorite, who utilized a tight guard to narrowly win the cleaner stanzas.
The audience's tolerance decreased during regular grabbing, with the challenger falling to the floor multiple occasions during grappling.
Parker ended stronger, but several stanzas were difficult to score. However, ex-champion the boxing analyst - providing analysis for the broadcast network - had it particularly wide for the challenger, giving Buatsi just a single round.
Buatsi advances, but with the likes of heavy hitter David Benavidez, and Eastern European fighter Dmitry Bivol ruling the division, the path to championship success - judging by this showing - still seems difficult.
Hatton Tribute Motivates Local Rivalry Contest
In the supporting bout, Arthur beat Rea by close verdict in a excellent all-Manchester contest to win the European light-heavyweight title.
The stadium became quiet for a extremely emotional homage ahead of the contest as 10 bells rang in remembrance of the city's native Ricky Hatton, who passed away 46 years old in September.
It was the premier televised boxing event in the city since the passing of Hatton. As the concluding sound disappeared, the silence became a roar of "there's just one Hatton".
The competition within the ring reflected the emotion. Arthur was knocked down by a left hook flush on the face in the early round, rising shakily to his footing on the count of eight.
But the traditional red attire of Arthur soon advanced again. On the opposite side, the opponent - in opposing blue - was injured quickly, heavy swelling developing under his face as the fighters landed punishing blows.
Rea, twenty-seven, landed power punches but the champion, 34, matched the intensity with effective uppercuts as the pace hardly diminished over the full distance.
Arthur narrowly won the verdict with judges scorecards of even score, close margin and wider gap, but the two athletes were relentless and courageous, all the qualities their idol Hatton stood for.
