British light heavyweight Buatsi secured a victory yet disappointing debut to life under new promoters with a unanimous decision over Zach Parker in Manchester.
The Olympic bronze medallist's work rate seemingly secured him a split decision in a tight 10-round contest at the Manchester venue.
But Parker landed significant shots, connecting with powerful individual punches in a contest where the approaches never quite clicked, with constant grabbing disrupting the contest.
Two judges scored it 96-94 for to Buatsi, with the remaining official a even score.
"It wasn't my greatest showing but what defines champions? They succeed," Buatsi commented in the ringside as he was faced disapproval from the spectators.
The Londoner returned to winning ways after his first professional defeat - an thrilling contest with Callum Smith in February - to earn a twentieth professional win.
Some ringside observers believed the challenger, 31, merited the win but the British boxer suffered the second setback of his 28-match career.
Buatsi Claims Triumph in Uneventful Encounter
His career development has stalled in the past few years through promotional disputes and considerable time of inactivity.
Earlier forecast as the next star of British boxing, he now finds himself trying to achieve expectations - maybe in what feels like a ultimate opportunity - under new promotional backing.
He started carefully, with both competitors willing to be aggressive in a cagey early stages.
The challenger, whose sole prior loss came at super middleweight against his former opponent in 2022 after breaking his hand during the bout, was participating in his second appearance at light heavyweight.
By the middle rounds, Parker had made it competitive, making life awkward for Buatsi, who operated with a protective stance to narrowly win the better stanzas.
The audience's tolerance wore thin during regular grabbing, with Parker going down various instances during grappling.
The underdog finished the stronger, but many rounds were difficult to score. Nevertheless, former world champion the boxing analyst - providing analysis for Dazn - had it particularly wide for Parker, awarding Buatsi just one round.
The victor progresses, but with the presence of hard hitter Benavidez, and Russian champion Bivol ruling the division, the road to world glory - judging by this showing - still seems difficult.
Ricky Hatton Memorial Inspires Local Rivalry Battle
In the supporting bout, Lyndon Arthur defeated Rea by divided decision in a terrific Manchester vs Manchester fight to win the continental title.
The arena became quiet for a profoundly moving memorial prior to the bout as ten bells tolled in memory of the city's native Ricky Hatton, who died 46 years old in last month.
It was the first major televised fight night in the city since Hatton's death. As the concluding sound ended, the quiet became a chant of "there's only one Ricky Hatton".
The action during the bout equaled the sentiment. The eventual winner was sent to the canvas by a significant blow flush on the face in the early round, standing uncertainly to his feet on the count of eight.
But the Manchester United-red attire of Arthur soon pressed ahead again. On the opposite side, the opponent - in opposing blue - was damaged quickly, significant bruising appearing under his face as the pair landed punishing blows.
Rea, twenty-seven, landed power punches but the champion, 34, responded in kind with stinging uppercuts as the action rarely dropped over 12 rounds.
Arthur edged the verdict with judges scorecards of even score, narrow lead and clearer margin, but each competitor were persistent and brave, exactly what their inspiration the legend stood for.
