UK light heavyweight Buatsi made a winning yet unimpressive debut to life under new promoters with a points victory over Zach Parker in Manchester.
The Olympic bronze medallist's punch output likely gained him a split decision in a close 10-round contest at the Co-op Live Arena.
But Parker landed significant shots, connecting with powerful individual punches in a match where the styles failed to mesh, with constant grabbing spoiling the action.
Two judges judged it 96-94 in favor to Buatsi, with the final judge a 95-95.
"It wasn't my best display but what do champions do? They succeed," the victor commented in the ringside as he was met by negative reactions from the crowd.
The Londoner got back to winning after his first professional defeat - an epic battle with Callum Smith in February - to claim a 20th career victory.
Several boxing experts believed Parker, 31, merited the win but the Derbyshire fighter suffered the second loss of his 28-fight professional journey.
Buatsi Earns Victory in Slow Match
Buatsi's progress has plateaued in recent times through contract problems and considerable time of inactivity.
Earlier forecast as the future of British boxing, he now stands trying to fulfil that early promise - perhaps in what feels like a last chance - under fresh management.
He opened tentatively, with both competitors ready to be aggressive in a calculated initial rounds.
Parker, whose only previous defeat came at the lower weight class against John Ryder in 2022 after damaging his hand during the bout, was participating in his second bout at the higher weight class.
By the halfway stage, the underdog had stayed in contention, causing problems for the favorite, who utilized a protective stance to edge the better periods.
The crowd's patience decreased amid constant clinching, with Parker falling to the floor multiple occasions during clinches.
Parker ended stronger, but multiple periods were difficult to score. Nevertheless, former world champion Carl Frampton - commentating on Dazn - had it particularly wide for the challenger, giving Buatsi just one round.
The victor progresses, but with the caliber of power puncher Benavidez, and Russian champion Dmitry Bivol leading the category, the journey to titles - based on this performance - still seems difficult.
Ricky Hatton Tribute Motivates Manchester Derby Contest
In the co-main event, Lyndon Arthur defeated Bradley Rea by split-decision in a terrific local rivalry fight to win the European light heavyweight belt.
The arena fell silent for a deeply poignant tribute before the fight as a bell ceremony rang in remembrance of the city's native Hatton, who passed away at age 46 in September.
It was the premier televised fight night in the location since Hatton's passing. As the final chime faded, the stillness gave way to a shout of "there's just one Hatton".
The fighting during the bout matched the feeling. The eventual winner was knocked down by a left hook directly to the chin in the initial stage, getting up unsteadily to his position on the count of eight.
But the Manchester United-red shorts of the fighter soon advanced again. On the opposite side, the opponent - in rival City blue - was damaged quickly, noticeable damage developing under his orbital area as the fighters exchanged powerful shots.
Rea, 27, delivered effective strikes but Arthur, 34, fought fire with fire with stinging uppercuts as the pace rarely dropped over the full distance.
Arthur narrowly won the result with official scores of draw, narrow lead and clearer margin, but both fighters were relentless and full of heart, exactly what their idol Hatton stood for.
