British light heavyweight Buatsi earned a win yet disappointing debut to his career under new promoters with a unanimous decision over Zach Parker in Manchester.
The Olympic medal winner's activity level likely gained him a majority decision in a competitive 10-round bout at the Manchester venue.
But Parker landed significant shots, landing some telling clean blows in a fight where the styles didn't complement each other, with constant grabbing disrupting the fight.
Two judges judged it 96-94 to the winner, with the third a even score.
"It wasn't my best showing but how do champions respond? They prevail," Buatsi commented in the ring as he was met by boos from the crowd.
The British fighter returned to winning ways after his first professional defeat - an thrilling contest with his previous opponent in last winter - to claim a 20th pro success.
Some ringside observers felt Parker, 31, should have been awarded the decision but the Derbyshire fighter endured the second setback of his 28-bout career.
Buatsi Earns Victory in Slow Affair
His career development has plateaued in recent times through contract problems and considerable time of lack of fights.
Earlier forecast as the next star of UK boxing, he now is positioned trying to fulfil that early promise - possibly in what seems like a last chance - under fresh management.
He opened tentatively, with the two boxers willing to take risks in a tentative initial rounds.
The challenger, whose only previous defeat came at super middleweight against his former opponent in 2022 after suffering a hand injury in the contest, was making just his second fight at light-heavyweight.
By the halfway stage, Parker had made it competitive, causing problems for Buatsi, who operated with a protective stance to barely take the cleaner rounds.
The audience's tolerance wore thin during frequent holding, with Parker going down several times during clinches.
The underdog ended stronger, but several stanzas were challenging to assess. However, former world champion Carl Frampton - working with the broadcast network - had it particularly wide for Parker, giving Buatsi just only one stanza.
The victor advances, but with the presence of hard hitter Benavidez, and Russian champion Bivol leading the category, the path to championship success - based on this performance - still looks steep.
Hatton Homage Motivates Manchester Derby Contest
In the supporting bout, Arthur defeated Bradley Rea by split-decision in a excellent all-Manchester fight to secure the European light-heavyweight title.
The stadium became quiet for a profoundly moving tribute ahead of the contest as 10 bells tolled in remembrance of the city's native Hatton, who died aged 46 in September.
It was the first major televised boxing event in the location since Hatton's death. As the concluding sound ended, the quiet transitioned to a shout of "there's only one Hatton".
The fighting during the bout reflected the sentiment. Arthur was knocked down by a significant blow flush on the chin in the early round, getting up unsteadily to his footing on the eight count.
But the red-colored attire of the fighter soon advanced again. On the opposite side, Rea - in rival City blue - was marked up quickly, noticeable damage appearing under his face as the duo traded punishing blows.
The challenger, 27, landed power punches but Arthur, 34, responded in kind with stinging uppercuts as the action rarely dropped over twelve rounds.
The victor edged the decision with scoring tallies of 114-114, 115-113 and 115-112, but each competitor were determined and courageous, everything their hero the legend embodied.
