UK light-heavyweight Buatsi earned a win yet underwhelming debut to his career under recent management with a unanimous decision over Zach Parker in Manchester.
The Olympic medal winner's punch output appeared to earn him a majority decision in a close 10-round fight at the Manchester venue.
But the challenger had his moments, connecting with powerful single shots in a fight where the techniques failed to mesh, with excessive holding spoiling the fight.
Two judges had it 96-94 for to Buatsi, with the third a even score.
"It wasn't my best display but what do champions do? They win," Buatsi stated in the ringside as he was faced boos from the audience.
The British fighter bounced back after his initial pro loss - an epic battle with his previous opponent in February - to earn a 20th pro success.
Various analysts thought the challenger, 31, deserved the victory but the contender suffered the second defeat of his 28-bout professional journey.
The Champion Secures Win in Dull Match
Buatsi's progress has slowed in recent times through contract problems and considerable time of inactivity.
Once tipped as the rising talent of UK boxing, he now is positioned trying to realize his potential - maybe in what appears to be a last chance - under recent support.
He opened tentatively, with both competitors prepared to take risks in a tentative early stages.
The challenger, whose only previous defeat came at super middleweight against his former opponent in 2022 after suffering a hand injury during the bout, was making just his second appearance at the higher weight class.
By the fight's midpoint, Parker had stayed in contention, causing problems for the favorite, who worked behind a tight guard to narrowly win the cleaner periods.
The crowd's patience decreased because of frequent holding, with the challenger falling to the floor various instances during clinches.
Parker ended stronger, but many rounds were challenging to assess. Nevertheless, former world champion the boxing analyst - providing analysis for Dazn - had it significantly in favor for Parker, giving Buatsi just only one stanza.
Buatsi moves on, but with the presence of heavy hitter Benavidez, and Eastern European fighter Dmitry Bivol dominating the weight class, the journey to titles - judging by this showing - still looks steep.
Hatton Tribute Motivates Local Rivalry Fight
In the secondary fight, Lyndon Arthur overcame Bradley Rea by split-decision in a excellent all-Manchester battle to capture the European light-heavyweight belt.
The venue fell silent for a profoundly moving homage before the fight as a bell ceremony rang in remembrance of Manchester's own Hatton, who succumbed 46 years old in last month.
It was the premier televised match card in the city since Hatton's passing. As the last bell disappeared, the quiet became a shout of "there's just one Ricky Hatton".
The fighting inside the ropes equaled the feeling. The eventual winner was floored by a left hook flush on the face in the second round, getting up unsteadily to his feet on the count of eight.
But the red-colored shorts of the fighter soon advanced again. Across the ring, Rea - in opposing blue - was marked up soon, noticeable damage forming under his face as the fighters landed punishing blows.
Rea, 27, landed power punches but Arthur, thirty-four, responded in kind with effective uppercuts as the action rarely dropped over twelve rounds.
The victor barely secured the result with scoring tallies of even score, 115-113 and clearer margin, but each competitor were determined and brave, exactly what their inspiration Hatton represented.
