UK light-heavyweight Buatsi made a winning yet disappointing beginning to life under new promoters with a decision win over Zach Parker in Manchester.
The Olympic medal winner's work rate appeared to earn him a judges' verdict in a close 10-round fight at the Co-op Live Arena.
But the challenger had his moments, connecting with powerful clean blows in a contest where the approaches failed to mesh, with frequent clinching disrupting the contest.
Two judges had it 96-94 to the winner, with the remaining official a even score.
"It wasn't my finest showing but how do champions respond? They prevail," the victor said in the arena as he was greeted with negative reactions from the crowd.
The British fighter bounced back after his initial pro loss - an memorable fight with his previous opponent in February - to earn a 20th pro success.
Various analysts felt Parker, thirty-one, should have been awarded the victory but the British boxer suffered the second defeat of his 28-fight professional journey.
Buatsi Secures Win in Uneventful Affair
His career development has slowed in the past few years through management issues and considerable time of lack of fights.
Previously predicted as the next star of UK boxing, he now finds himself trying to realize his potential - maybe in what feels like a ultimate opportunity - under new promotional backing.
He started carefully, with neither fighter ready to be aggressive in a cagey early stages.
The challenger, whose only previous defeat came at the lower weight class against his former opponent in two years ago after suffering a hand injury in the contest, was participating in his second appearance at the higher weight class.
By the fight's midpoint, the underdog had stayed in contention, causing problems for the favorite, who utilized a tight guard to edge the cleaner periods.
The spectators' acceptance decreased because of regular grabbing, with the challenger falling to the floor multiple occasions during grappling.
The underdog ended stronger, but multiple periods were difficult to score. However, former world champion the boxing analyst - providing analysis for the broadcast network - had it strongly leaning for the challenger, giving Buatsi just one round.
Buatsi advances, but with the presence of hard hitter Benavidez, and Russian champion Dmitry Bivol leading the category, the path to championship success - based on this performance - still looks steep.
Hatton Memorial Fuels Local Rivalry Contest
In the co-main event, Lyndon Arthur defeated Rea by divided decision in a excellent all-Manchester contest to secure the continental championship.
The stadium fell silent for a deeply poignant memorial before the fight as a bell ceremony sounded in memory of the city's native Hatton, who passed away 46 years old in September.
It was the first major televised boxing event in the location since Hatton's passing. As the concluding sound faded, the stillness transitioned to a roar of "only one Ricky Hatton".
The action within the ring matched the emotion. Arthur was sent to the canvas by a significant blow flush on the chin in the early round, rising shakily to his position on the eight count.
But the red-colored shorts of the fighter soon advanced again. From the other corner, Rea - in opposing blue - was injured early, significant bruising appearing under his orbital area as the fighters exchanged hard punches.
The challenger, twenty-seven, landed power punches but Arthur, 34, matched the intensity with stinging uppercuts as the intensity rarely dropped over twelve rounds.
The victor barely secured the verdict with judges scorecards of even score, close margin and wider gap, but both fighters were determined and brave, all the qualities their idol Hatton embodied.
