British light heavyweight Buatsi made a winning yet disappointing beginning to his career under new promoters with a points victory over Zach Parker in Manchester.
The Olympic medal winner's punch output seemingly secured him a split decision in a tight 10-round bout at the Manchester venue.
But Parker had his moments, delivering effective single shots in a fight where the approaches failed to mesh, with constant grabbing spoiling the contest.
Two judges had it 96-94 to the winner, with the third a even score.
"It wasn't my finest performance but what defines champions? They win," Buatsi commented in the arena as he was greeted with disapproval from the audience.
The British fighter got back to winning after his initial pro loss - an memorable fight with Callum Smith in February - to earn a 20th pro success.
Several boxing experts believed the challenger, thirty-one, deserved the decision but the Derbyshire fighter experienced the second setback of his 28-match career.
The Champion Claims Win in Slow Affair
The fighter's advancement has slowed in recent times through management issues and considerable time of inactivity.
Previously predicted as the rising talent of UK boxing, he now is positioned trying to achieve expectations - maybe in what seems like a ultimate opportunity - under recent support.
He began cautiously, with the two boxers willing to be aggressive in a cagey initial rounds.
Parker, whose sole prior loss came at the lower weight class against John Ryder in 2022 after suffering a hand injury in the contest, was competing in only his second fight at the higher weight class.
By the halfway stage, the underdog had made it competitive, making life awkward for the favorite, who utilized a solid defense to edge the more effective periods.
The crowd's patience wore thin because of regular grabbing, with Parker going down multiple occasions during clinches.
The underdog ended stronger, but multiple periods were challenging to assess. Although, ex-champion Carl Frampton - commentating on the broadcast network - had it strongly leaning for Parker, giving Buatsi just one round.
Buatsi advances, but with the presence of hard hitter Benavidez, and Eastern European fighter Bivol ruling the division, the road to world glory - judging by this showing - still looks steep.
Hatton Memorial Motivates Manchester Derby Battle
In the secondary fight, Arthur overcame Bradley Rea by divided decision in a terrific all-Manchester contest to secure the European light heavyweight belt.
The stadium fell silent for a profoundly moving tribute prior to the bout as 10 bells tolled in honor of the city's native Ricky Hatton, who succumbed at age 46 in September.
It was the premier televised boxing event in the urban center since Hatton's death. As the final chime ended, the quiet became a roar of "there's only one Ricky Hatton".
The competition inside the ropes reflected the feeling. Arthur was knocked down by a powerful punch directly to the chin in the second round, getting up unsteadily to his position on the referee's count.
But the traditional red shorts of Arthur soon came forward again. From the other corner, Rea - in opposing blue - was damaged quickly, heavy swelling developing under his eye as the pair landed hard punches.
The challenger, 27, connected with strong blows but Arthur, 34, fought fire with fire with effective uppercuts as the action hardly diminished over twelve rounds.
The victor edged the decision with official scores of 114-114, 115-113 and clearer margin, but the two athletes were determined and courageous, everything their hero Hatton embodied.
