UK light-heavyweight Buatsi made a winning yet underwhelming start to his career under fresh promotional backing with a points victory over Zach Parker in Manchester.
The Olympic medal winner's work rate seemingly secured him a majority decision in a close ten-round fight at the Manchester venue.
But Parker found success, delivering effective clean blows in a fight where the approaches failed to mesh, with excessive holding disrupting the fight.
The officials scored it 96-94 for to the winner, with the third a 95-95 draw.
"It wasn't my best performance but what defines champions? They prevail," Buatsi said in the ring as he was met by boos from the spectators.
The British fighter got back to winning after his maiden career setback - an epic battle with Callum Smith in February - to secure a 20th pro success.
Various analysts believed the challenger, thirty-one, merited the victory but the Derbyshire fighter suffered the second loss of his 28-match career.
Buatsi Secures Victory in Slow Affair
Buatsi's progress has slowed in recent times through promotional disputes and long spells of lack of fights.
Earlier forecast as the future of British boxing, he now stands trying to fulfil that early promise - possibly in what seems like a ultimate opportunity - under new promotional backing.
He began cautiously, with neither fighter willing to be aggressive in a tentative initial rounds.
Parker, whose single earlier setback came at the lower weight class against John Ryder in 2022 after suffering a hand injury mid-fight, was participating in his second fight at light-heavyweight.
By the fight's midpoint, Parker had made it competitive, causing problems for Buatsi, who worked behind a solid defense to narrowly win the better stanzas.
The spectators' acceptance wore thin amid constant clinching, with Parker falling to the floor multiple occasions during clinches.
The underdog finished the stronger, but several stanzas were hard to judge. Although, former world champion Carl Frampton - providing analysis for the broadcast network - had it strongly leaning for the challenger, giving Buatsi just only one stanza.
The victor progresses, but with the likes of heavy hitter David Benavidez, and Eastern European fighter Bivol dominating the weight class, the journey to titles - on this evidence - still seems difficult.
Ricky Hatton Tribute Fuels Local Rivalry Fight
In the co-main event, Arthur defeated Rea by divided decision in a terrific Manchester vs Manchester battle to win the European light-heavyweight belt.
The arena became quiet for a extremely emotional homage prior to the bout as 10 bells rang in honor of Manchester's own Hatton, who passed away aged 46 in last month.
It was the premier televised boxing event in the location since Hatton's passing. As the last bell disappeared, the quiet gave way to a shout of "there's just one Ricky Hatton".
The competition during the bout equaled the emotion. Arthur was knocked down by a significant blow directly to the jaw in the initial stage, getting up unsteadily to his feet on the count of eight.
But the red-colored attire of the fighter soon pressed ahead again. Across the ring, the opponent - in rival City blue - was damaged early, noticeable damage developing under his orbital area as the fighters traded powerful shots.
Rea, 27, connected with strong blows but the champion, 34, fought fire with fire with stinging uppercuts as the action seldom decreased over 12 rounds.
Arthur edged the result with official scores of even score, close margin and clearer margin, but each competitor were persistent and full of heart, exactly what their inspiration the legend represented.
