UK light heavyweight Buatsi made a winning yet unimpressive beginning to his career under recent management with a unanimous decision over Zach Parker in the Manchester arena.
The Olympic bronze medallist's work rate likely gained him a judges' verdict in a close 10-round bout at the Co-op Live Arena.
But Parker found success, landing some telling individual punches in a fight where the techniques never quite clicked, with frequent clinching marring the fight.
Two judges scored it 96-94 in favor to Buatsi, with the remaining official a even score.
"It wasn't my greatest display but how do champions respond? They succeed," Buatsi commented in the ring as he was faced disapproval from the crowd.
The British fighter 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 felt Parker, thirty-one, merited the decision but the Derbyshire fighter experienced the second setback of his 28-match professional journey.
The Champion Claims Win in Slow Match
The fighter's advancement has slowed in recent times through management issues and long spells of inactivity.
Once tipped as the future of British boxing, he now finds himself trying to fulfil that early promise - maybe in what appears to be a ultimate opportunity - under fresh management.
He started carefully, with the two boxers prepared to be aggressive in a calculated initial rounds.
The challenger, whose single earlier setback came at super-middleweight against his former opponent in 2022 after damaging his hand during the bout, was making just his second fight at the higher weight class.
By the halfway stage, Parker had stayed in contention, causing problems for the favorite, who utilized a protective stance to narrowly win the more effective periods.
The crowd's patience wore thin because of constant clinching, with the challenger slipping to the canvas several times during grappling.
Parker closed well, but many rounds were difficult to score. However, previous titleholder Carl Frampton - providing analysis for Dazn - had it strongly leaning for Parker, scoring for Buatsi just one round.
Buatsi advances, but with the caliber of power puncher Benavidez, and Eastern European fighter Bivol dominating the weight class, the journey to titles - on this evidence - still looks steep.
Ricky Hatton Memorial Fuels Manchester Derby Battle
In the secondary fight, Lyndon Arthur overcame Bradley Rea by close verdict in a terrific Manchester vs Manchester battle to secure the European light-heavyweight championship.
The venue fell silent for a extremely emotional tribute before the fight as 10 bells tolled in honor of the city's native Ricky Hatton, who died aged 46 in last month.
It was the first major televised boxing event in the urban center since Hatton's passing. As the final chime disappeared, the silence became a shout of "only one Ricky Hatton".
The action within the ring reflected the sentiment. The eventual winner was knocked down by a significant blow flush on the face in the early round, rising shakily to his position on the eight count.
But the Manchester United-red attire of the fighter soon came forward again. Across the ring, the opponent - in rival City blue - was marked up soon, significant bruising developing under his eye as the fighters traded powerful shots.
The challenger, twenty-seven, connected with strong blows but the champion, 34, fought fire with fire with stinging uppercuts as the intensity rarely dropped over twelve rounds.
The victor barely secured the decision with judges scorecards of even score, close margin and wider gap, but both fighters were determined and brave, all the qualities their hero the legend embodied.
