UK light-heavyweight Buatsi made a winning yet disappointing beginning to his career under recent management with a unanimous decision over Zach Parker in Manchester.
The Olympic medal winner's activity level appeared to earn him a majority decision in a tight 10-round fight at the Co-op Live Arena.
But Parker landed significant shots, delivering effective single shots in a contest where the techniques never quite clicked, with constant grabbing spoiling the contest.
Two judges had it 96-94 for to Buatsi, with the remaining official a 95-95.
"It wasn't my finest display but what defines champions? They win," the victor commented in the arena as he was met by negative reactions from the audience.
The British fighter got back to winning after his first professional defeat - an memorable fight with his previous opponent in February - to secure a 20th career victory.
Some ringside observers believed Parker, thirty-one, merited the win but the contender endured the second defeat of his 28-match professional journey.
Buatsi Secures Win in Slow Encounter
Buatsi's progress has stalled in the past few years through contract problems and extended periods of inactivity.
Previously predicted as the future of British boxing, he now finds himself trying to fulfil that early promise - possibly in what seems like a final roll of the dice - under new promotional backing.
He began cautiously, with both competitors ready to take risks in a calculated early stages.
Parker, whose sole prior loss came at the lower weight class against his former opponent in two years ago after breaking his hand in the contest, was competing in only his second appearance at the higher weight class.
By the middle rounds, the underdog had made it competitive, causing problems for Buatsi, who worked behind a protective stance to barely take the cleaner rounds.
The audience's tolerance wore thin during regular grabbing, with the challenger going down multiple occasions during grappling.
Parker closed well, but many rounds were hard to judge. However, former world champion Carl Frampton - commentating on Dazn - had it particularly wide for Parker, awarding Buatsi just one round.
The victor moves on, but with the likes of power puncher Benavidez, and Russian star Dmitry Bivol leading the category, the path to championship success - based on this performance - still appears challenging.
Ricky Hatton Tribute Inspires All-Manchester Fight
In the supporting bout, Arthur beat Bradley Rea by split-decision in a terrific all-Manchester battle to secure the continental championship.
The venue fell silent for a profoundly moving memorial ahead of the contest as 10 bells tolled in memory of the city's native Hatton, who passed away aged 46 in recently.
It was the first major televised fight night in the location since the passing of Hatton. As the last bell disappeared, the stillness transitioned to a chant of "only one Hatton".
The competition within the ring reflected the sentiment. The eventual winner was floored by a significant blow flush on the chin in the early round, rising shakily to his position on the eight count.
But the traditional red equipment of Arthur soon came forward again. From the other corner, the opponent - in rival City blue - was injured early, heavy swelling appearing under his orbital area as the pair exchanged powerful shots.
The challenger, twenty-seven, landed power punches but Arthur, 34, matched the intensity with powerful upward punches as the pace rarely dropped over 12 rounds.
The victor edged the verdict with scoring tallies of even score, close margin and 115-112, but both fighters were relentless and brave, exactly what their hero the legend embodied.
