UK light heavyweight Buatsi earned a win yet disappointing debut to life under fresh promotional backing with a points victory over Zach Parker in Manchester.
The Olympic bronze medallist's activity level likely gained him a split decision in a close ten-round contest at the Co-op Live Arena.
But the challenger found success, delivering effective single shots in a fight where the techniques failed to mesh, with frequent clinching marring the fight.
The scoring judges judged it 96-94 in favor to the winner, with the remaining official a 95-95.
"It wasn't my greatest showing but what defines champions? They win," the victor commented in the ring as he was met by negative reactions from the audience.
The Londoner returned to winning ways after his initial pro loss - an epic battle with Callum Smith in February - to earn a twentieth professional win.
Various analysts believed the challenger, thirty-one, merited the victory but the Derbyshire fighter endured the second loss of his 28-match career.
Buatsi Earns Win in Slow Match
His career development has plateaued in the past few years through promotional disputes and extended periods of lack of fights.
Once tipped as the rising talent of British boxing, he now is positioned trying to achieve expectations - possibly in what feels like a last chance - under new promotional backing.
He opened tentatively, with the two boxers prepared to be aggressive in a calculated opening few rounds.
Parker, whose sole prior loss came at super middleweight against John Ryder in 2022 after breaking his hand mid-fight, was participating in his second bout at the higher weight class.
By the halfway stage, the underdog had made it competitive, making life awkward for Buatsi, who utilized a protective stance to edge the better rounds.
The crowd's patience diminished during frequent holding, with the challenger slipping to the canvas various instances during grappling.
The underdog finished the stronger, but multiple periods were difficult to score. However, ex-champion Carl Frampton - commentating on Dazn - had it strongly leaning for the challenger, scoring for Buatsi just one round.
Buatsi progresses, but with the likes of heavy hitter David Benavidez, and Russian star Bivol leading the category, the journey to titles - judging by this showing - still appears challenging.
Hatton Memorial Fuels Local Rivalry Contest
In the supporting bout, Arthur beat Rea by divided decision in a outstanding all-Manchester fight to secure the European light heavyweight championship.
The stadium became quiet for a profoundly moving homage ahead of the contest as ten bells rang in memory of Manchester's own Ricky Hatton, who passed away at age 46 in last month.
It was the first major televised match card in the urban center since the passing of Hatton. As the last bell ended, the stillness gave way to a roar of "there's just one Hatton".
The fighting during the bout reflected the sentiment. Arthur was sent to the canvas by a powerful punch directly to the jaw in the early round, rising shakily to his position on the eight count.
But the traditional red shorts of the fighter soon came forward again. On the opposite side, the opponent - in competitive blue - was injured quickly, heavy swelling developing under his eye as the pair traded hard punches.
Rea, twenty-seven, delivered effective strikes but Arthur, 34, fought fire with fire with stinging uppercuts as the action seldom decreased over twelve rounds.
Arthur barely secured the result with official scores of even score, close margin and 115-112, but each competitor were determined and full of heart, everything their inspiration Hatton stood for.
