British light heavyweight Buatsi earned a win yet unimpressive debut to his career under new promoters with a points victory over Zach Parker in Manchester.
The Olympic medal winner's activity level likely gained him a split decision in a tight 10-round contest at the boxing arena.
But Parker landed significant shots, delivering effective single shots in a match where the techniques didn't complement each other, with excessive holding marring the contest.
The officials judged it 96-94 in favor to Buatsi, with the final judge a 95-95.
"It wasn't my finest showing but how do champions respond? They win," Buatsi said in the arena as he was faced negative reactions from the audience.
The Londoner got back to winning after his maiden career setback - an thrilling contest with Callum Smith in February - to secure a twentieth professional win.
Various analysts believed Parker, 31, merited the victory but the Derbyshire fighter endured the second loss of his 28-fight career.
Buatsi Secures Win in Dull Encounter
His career development has plateaued in the past few years through promotional disputes and extended periods of inactivity.
Earlier forecast as the future of British boxing, he now finds himself trying to achieve expectations - perhaps in what feels like a ultimate opportunity - under fresh management.
He opened tentatively, with the two boxers ready to be aggressive in a tentative initial rounds.
The challenger, whose only previous defeat came at the lower weight class against John Ryder in 2022 after damaging his hand mid-fight, was competing in only his second fight at the higher weight class.
By the halfway stage, the underdog had kept it close, causing problems for Buatsi, who operated with a protective stance to narrowly win the more effective rounds.
The audience's tolerance decreased because of constant clinching, with the challenger going down multiple occasions during clinches.
The underdog ended stronger, but many rounds were hard to judge. However, ex-champion the boxing analyst - commentating on Dazn - had it strongly leaning for the challenger, awarding Buatsi just only one stanza.
The victor progresses, but with the presence of power puncher David Benavidez, and Eastern European fighter Dmitry Bivol dominating the weight class, the journey to titles - judging by this showing - still seems difficult.
Ricky Hatton Homage Inspires Local Rivalry Contest
In the supporting bout, Arthur defeated Rea by divided decision in a excellent local rivalry contest to capture the continental title.
The venue became quiet for a extremely emotional tribute ahead of the contest as ten bells rang in memory of local hero Ricky Hatton, who died 46 years old in recently.
It was the first major televised boxing event in the urban center since Hatton's passing. As the concluding sound ended, the quiet transitioned to a chant of "there's only one Ricky Hatton".
The fighting within the ring equaled the emotion. The eventual winner was knocked down by a left hook directly to the chin in the second round, standing uncertainly to his feet on the referee's count.
But the traditional red attire of the fighter soon advanced again. Across the ring, the opponent - in opposing blue - was marked up early, significant bruising appearing under his face as the fighters traded hard punches.
Rea, twenty-seven, landed power punches but the champion, 34, fought fire with fire with stinging uppercuts as the pace seldom decreased over 12 rounds.
The victor edged the verdict with scoring tallies of 114-114, narrow lead and clearer margin, but each competitor were relentless and courageous, everything their inspiration the legend stood for.
