UK light heavyweight Buatsi made a winning yet disappointing beginning to life under fresh promotional backing with a unanimous decision over Zach Parker in Manchester.
The Olympic medal winner's punch output appeared to earn him a split decision in a competitive 10-round contest at the Manchester venue.
But the challenger landed significant shots, delivering effective individual punches in a match where the approaches failed to mesh, with frequent clinching marring the action.
The officials judged it 96-94 to Buatsi, with the third a 95-95 draw.
"It wasn't my greatest showing but what do champions do? They succeed," Buatsi stated in the ringside as he was met by boos from the audience.
The British fighter bounced back after his first professional defeat - an memorable fight with Callum Smith in February - to earn a twentieth professional win.
Various analysts thought the challenger, 31, should have been awarded the victory but the contender suffered the second defeat of his 28-match professional journey.
The Champion Earns Triumph in Uneventful Encounter
His career development has plateaued in the past few years through promotional disputes and long spells of lack of fights.
Earlier forecast as the next star of British boxing, he now stands trying to realize his potential - maybe in what appears to be a last chance - under new promotional backing.
He opened tentatively, with neither fighter ready to be aggressive in a cagey opening few rounds.
The challenger, whose only previous defeat came at super-middleweight against his former opponent in two years ago after damaging his hand during the bout, was participating in his second bout at light-heavyweight.
By the halfway stage, the underdog had kept it close, causing problems for Buatsi, who operated with a solid defense to narrowly win the more effective stanzas.
The crowd's patience decreased amid constant clinching, with Parker slipping to the canvas several times during grappling.
Parker closed well, but multiple periods were difficult to score. Although, previous titleholder the boxing analyst - working with Dazn - had it particularly wide for the challenger, awarding Buatsi just a single round.
Buatsi progresses, but with the caliber of power puncher David Benavidez, and Eastern European fighter Dmitry Bivol leading the category, the path to championship success - based on this performance - still looks steep.
Ricky Hatton Homage Fuels Manchester Derby Fight
In the co-main event, Arthur overcame Rea by divided decision in a excellent local rivalry battle to secure the European light heavyweight belt.
The stadium became quiet for a deeply poignant homage before the fight as 10 bells tolled in honor of the city's native Ricky Hatton, who died 46 years old in last month.
It was the first major televised match card in the urban center since the passing of Hatton. As the last bell ended, the stillness transitioned to a chant of "only one Ricky Hatton".
The competition during the bout reflected the feeling. The eventual winner was sent to the canvas by a powerful punch flush on the chin in the second round, rising shakily to his footing on the referee's count.
But the traditional red equipment of the fighter soon pressed ahead again. Across the ring, Rea - in competitive blue - was injured quickly, noticeable damage developing under his eye as the fighters landed punishing blows.
Rea, twenty-seven, connected with strong blows but Arthur, thirty-four, matched the intensity with powerful upward punches as the pace seldom decreased over the full distance.
Arthur edged the result with judges scorecards of 114-114, 115-113 and wider gap, but each competitor were relentless and full of heart, everything their idol Hatton stood for.
