British light heavyweight Buatsi earned a win yet underwhelming start to his career under new promoters with a unanimous decision over Zach Parker in Manchester.
The Olympic bronze medallist's work rate seemingly secured him a majority decision in a competitive ten-round fight at the Co-op Live Arena.
But Parker had his moments, landing some telling individual punches in a contest where the styles never quite clicked, with constant grabbing marring the fight.
The officials scored it 96-94 for to Buatsi, with the final judge a 95-95.
"It wasn't my best performance but how do champions respond? They prevail," the victor said in the ringside as he was met by negative reactions from the crowd.
The Londoner returned to winning ways after his maiden career setback - an epic battle with Callum Smith in February - to earn a twentieth professional win.
Various analysts believed Parker, 31, should have been awarded the decision but the British boxer experienced the second loss of his 28-match professional journey.
The Champion Claims Victory in Slow Encounter
His career development has stalled in recent times through contract problems and extended periods of inactivity.
Earlier forecast as the future of the British fight scene, he now is positioned trying to achieve expectations - possibly in what feels like a last chance - under fresh management.
He opened tentatively, with both competitors ready to be aggressive in a cagey early stages.
The challenger, whose single earlier setback came at super-middleweight against John Ryder in two years ago after damaging his hand during the bout, was competing in only his second appearance at the higher weight class.
By the middle rounds, Parker had stayed in contention, making life awkward for Buatsi, who operated with a tight guard to edge the more effective periods.
The audience's tolerance diminished because of regular grabbing, with Parker falling to the floor multiple occasions during close exchanges.
Parker closed well, but multiple periods were challenging to assess. Although, previous titleholder Carl Frampton - providing analysis for Dazn - had it significantly in favor for Parker, scoring for Buatsi just one round.
Buatsi moves on, but with the presence of power puncher Benavidez, and Russian star Dmitry Bivol leading the category, the path to championship success - judging by this showing - still appears challenging.
Hatton Homage Motivates Local Rivalry Battle
In the secondary fight, Lyndon Arthur beat Bradley Rea by close verdict in a terrific local rivalry battle to capture the European light heavyweight title.
The arena became quiet for a deeply poignant tribute ahead of the contest as ten bells tolled in honor of the city's native Ricky Hatton, who died 46 years old in September.
It was the initial significant broadcast boxing event in the location since the passing of Hatton. As the last bell ended, the quiet became a shout of "there's just one Ricky Hatton".
The action within the ring reflected the sentiment. Arthur was sent to the canvas by a significant blow directly to the chin in the second round, rising shakily to his position on the count of eight.
But the traditional red equipment of the fighter soon advanced again. From the other corner, Rea - in opposing blue - was marked up soon, significant bruising developing under his eye as the pair exchanged powerful shots.
The challenger, 27, connected with strong blows but the champion, thirty-four, fought fire with fire with stinging uppercuts as the pace hardly diminished over twelve rounds.
Arthur barely secured the decision with judges scorecards of 114-114, narrow lead and clearer margin, but each competitor were persistent and courageous, everything their idol Hatton embodied.
