British light-heavyweight Buatsi secured a victory yet disappointing start to his career under fresh promotional backing with a unanimous decision over Zach Parker in the Manchester arena.
The Olympic medal winner's activity level seemingly secured him a split decision in a competitive 10-round fight at the boxing arena.
But Parker found success, connecting with powerful single shots in a contest where the techniques never quite clicked, with frequent clinching marring the fight.
Two judges scored it 96-94 in favor to Buatsi, with the third a 95-95.
"It wasn't my best performance but how do champions respond? They prevail," the victor said in the arena as he was met by negative reactions from the spectators.
The British fighter got back to winning after his first professional defeat - an epic battle with Callum Smith in February - to secure a twentieth professional win.
Various analysts thought the challenger, thirty-one, should have been awarded the win but the Derbyshire fighter suffered the second setback of his 28-match professional journey.
The Champion Claims Victory in Slow Affair
The fighter's advancement has plateaued in recent years through promotional disputes and long spells of lack of fights.
Previously predicted as the future of UK boxing, he now stands trying to achieve expectations - maybe in what appears to be a last chance - under new promotional backing.
He began cautiously, with the two boxers prepared to be aggressive in a tentative early stages.
Parker, whose sole prior loss came at super-middleweight against John Ryder in 2022 after breaking his hand in the contest, was participating in his second appearance at the higher weight class.
By the middle rounds, the underdog had stayed in contention, making life awkward for Buatsi, who worked behind a protective stance to narrowly win the more effective stanzas.
The audience's tolerance diminished during constant clinching, with Parker going down several times during close exchanges.
The underdog finished the stronger, but many rounds were challenging to assess. Nevertheless, former world champion Carl Frampton - working with Dazn - had it strongly leaning for Parker, giving Buatsi just only one stanza.
Buatsi advances, but with the presence of power puncher Benavidez, and Russian star Bivol leading the category, the journey to titles - on this evidence - still looks steep.
Hatton Memorial Inspires All-Manchester Fight
In the supporting bout, Lyndon Arthur defeated Rea by close verdict in a terrific local rivalry contest to secure the continental championship.
The stadium became quiet for a extremely emotional homage prior to the bout as a bell ceremony sounded in honor of the city's native Ricky Hatton, who passed away 46 years old in September.
It was the premier televised match card in the city since Hatton's death. As the last bell faded, the quiet became a chant of "there's just one Ricky Hatton".
The action within the ring reflected the emotion. Arthur was knocked down by a powerful punch flush on the jaw in the early round, standing uncertainly to his position on the count of eight.
But the red-colored equipment of the fighter soon pressed ahead again. From the other corner, Rea - in opposing blue - was injured quickly, noticeable damage appearing under his eye as the pair traded powerful shots.
Rea, twenty-seven, connected with strong blows but the champion, thirty-four, fought fire with fire with effective uppercuts as the intensity hardly diminished over 12 rounds.
Arthur edged the verdict with scoring tallies of even score, close margin and wider gap, but each competitor were relentless and courageous, all the qualities their hero Hatton represented.
