UK light-heavyweight Buatsi secured a victory yet disappointing start to his career under fresh promotional backing with a unanimous decision over Zach Parker in Manchester.
The Olympic bronze medallist's activity level appeared to earn him a split decision in a competitive ten-round fight at the boxing arena.
But Parker had his moments, connecting with powerful clean blows in a match where the styles failed to mesh, with constant grabbing marring the contest.
The scoring judges judged it 96-94 to the winner, with the remaining official a even score.
"It wasn't my best display but what do champions do? They win," Buatsi stated in the ring as he was greeted with disapproval from the crowd.
The British fighter got back to winning after his initial pro loss - an memorable fight with his previous opponent in February - to secure a 20th pro success.
Various analysts thought the challenger, 31, should have been awarded the win but the contender endured the second defeat of his 28-bout professional journey.
The Champion Secures Triumph in Slow Match
The fighter's advancement has stalled in recent years through management issues and long spells of inactivity.
Earlier forecast as the rising talent of UK boxing, he now stands trying to realize his potential - possibly in what feels like a final roll of the dice - under fresh management.
He opened tentatively, with neither fighter prepared to be aggressive in a calculated 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 during the bout, was competing in only his second fight at light heavyweight.
By the halfway stage, Parker had made it competitive, creating difficulties for the favorite, who operated with a protective stance to narrowly win the cleaner periods.
The crowd's patience decreased during frequent holding, with Parker falling to the floor several times during grappling.
The underdog finished the stronger, but many rounds were hard to judge. Nevertheless, ex-champion the boxing analyst - commentating on Dazn - had it strongly leaning for Parker, awarding Buatsi just only one stanza.
Buatsi moves on, but with the caliber of heavy hitter Benavidez, and Eastern European fighter Dmitry Bivol dominating the weight class, the path to championship success - based on this performance - still seems difficult.
Ricky Hatton Memorial Motivates Manchester Derby Contest
In the co-main event, Lyndon Arthur overcame Bradley Rea by close verdict in a terrific all-Manchester contest to win the European light heavyweight championship.
The venue fell silent for a extremely emotional tribute prior to the bout as ten bells rang in honor of Manchester's own Hatton, who passed away 46 years old in recently.
It was the premier televised boxing event in the urban center since Hatton's death. As the final chime ended, the stillness became a roar of "only one Ricky Hatton".
The competition within the ring reflected the feeling. The eventual winner was sent to the canvas by a powerful punch flush on the chin in the early round, getting up unsteadily to his feet on the eight count.
But the red-colored equipment of Arthur soon came forward again. On the opposite side, the opponent - in rival City blue - was damaged quickly, noticeable damage forming under his eye as the duo traded hard punches.
The challenger, 27, landed power punches but Arthur, 34, fought fire with fire with powerful upward punches as the action rarely dropped over twelve rounds.
The victor edged the verdict with judges scorecards of 114-114, narrow lead and 115-112, but both fighters were relentless and courageous, all the qualities their hero the legend stood for.
