British light heavyweight Buatsi made a winning yet underwhelming start to his career under fresh promotional backing with a decision win over Zach Parker in the Manchester arena.
The Olympic bronze medallist's punch output seemingly secured him a majority decision in a close 10-round contest at the Manchester venue.
But Parker had his moments, connecting with powerful individual punches in a contest where the styles never quite clicked, with constant grabbing marring the contest.
Two judges judged it 96-94 to the winner, with the final judge a even score.
"It wasn't my best showing but how do champions respond? They succeed," the victor said in the ringside as he was greeted with disapproval from the audience.
The Londoner bounced back after his initial pro loss - an memorable fight with Callum Smith in last winter - to claim a 20th pro success.
Various analysts felt Parker, 31, deserved the victory but the Derbyshire fighter endured the second setback of his 28-bout career.
Buatsi Earns Triumph in Dull Encounter
His career development has slowed in recent times through contract problems and extended periods of inactivity.
Once tipped as the future of UK boxing, he now finds himself trying to realize his potential - perhaps in what appears to be a ultimate opportunity - under new promotional backing.
He opened tentatively, with both competitors willing to take risks in a cagey opening few rounds.
Parker, whose only previous defeat came at super middleweight against his former opponent in two years ago after breaking his hand during the bout, was competing in only his second fight at the higher weight class.
By the fight's midpoint, the underdog had kept it close, creating difficulties for the favorite, who worked behind a protective stance to barely take the cleaner stanzas.
The audience's tolerance wore thin amid regular grabbing, with the challenger going down several times during close exchanges.
The underdog ended stronger, but many rounds were challenging to assess. Although, previous titleholder the boxing analyst - working with the broadcast network - had it significantly in favor for the challenger, giving Buatsi just a single round.
The victor advances, but with the caliber of heavy hitter Benavidez, and Eastern European fighter Dmitry Bivol dominating the weight class, the road to world glory - judging by this showing - still seems difficult.
Ricky Hatton Memorial Motivates All-Manchester Fight
In the co-main event, Lyndon Arthur overcame Rea by divided decision in a terrific local rivalry battle to capture the European light-heavyweight belt.
The arena grew hushed for a profoundly moving homage ahead of the contest as 10 bells rang in honor of the city's native Ricky Hatton, who succumbed aged 46 in last month.
It was the premier televised match card in the urban center since the passing of Hatton. As the final chime faded, the stillness gave way to a shout of "only one Ricky Hatton".
The fighting during the bout equaled the feeling. Arthur was knocked down by a significant blow flush on the face in the initial stage, standing uncertainly to his footing on the count of eight.
But the red-colored shorts of Arthur soon pressed ahead again. On the opposite side, the opponent - in competitive blue - was damaged quickly, noticeable damage developing under his face as the pair exchanged hard punches.
The challenger, 27, landed power punches but the champion, thirty-four, responded in kind with effective uppercuts as the intensity seldom decreased over 12 rounds.
Arthur narrowly won the decision with official scores of 114-114, narrow lead and wider gap, but the two athletes were persistent and courageous, exactly what their hero Hatton represented.
