UK light heavyweight Buatsi earned a win yet disappointing beginning to his career under fresh promotional backing with a unanimous decision over Zach Parker in Manchester.
The Olympic medal winner's punch output likely gained him a majority decision in a competitive 10-round contest at the Manchester venue.
But Parker had his moments, delivering effective individual punches in a fight where the approaches failed to mesh, with excessive holding spoiling the fight.
The scoring judges judged it 96-94 in favor to the winner, with the remaining official a 95-95.
"It wasn't my greatest performance but what defines champions? They win," Buatsi stated in the arena as he was greeted with disapproval from the audience.
The British fighter bounced back after his maiden career setback - an thrilling contest with Callum Smith in February - to claim a 20th pro success.
Some ringside observers thought Parker, thirty-one, merited the decision but the Derbyshire fighter endured the second defeat of his 28-bout career.
The Champion Earns Victory in Uneventful Affair
The fighter's advancement has plateaued in recent years through contract problems and long spells of inactivity.
Earlier forecast as the next star of British boxing, he now stands trying to achieve expectations - possibly in what appears to be a last chance - under recent support.
He started carefully, with both competitors ready to take risks in a cagey early stages.
The challenger, whose single earlier setback came at super-middleweight against John Ryder in two years ago after damaging his hand during the bout, was making just his second bout at light-heavyweight.
By the fight's midpoint, the underdog had kept it close, causing problems for the favorite, who worked behind a tight guard to barely take the cleaner stanzas.
The audience's tolerance diminished because of constant clinching, with the challenger falling to the floor several times during clinches.
The underdog closed well, but many rounds were hard to judge. However, former world champion the boxing analyst - working with the broadcast network - had it particularly wide for the challenger, scoring for Buatsi just only one stanza.
The victor progresses, but with the likes of power puncher David Benavidez, and Eastern European fighter Dmitry Bivol dominating the weight class, the journey to titles - judging by this showing - still seems difficult.
Ricky Hatton Tribute Fuels Manchester Derby Contest
In the supporting bout, Arthur overcame Bradley Rea by split-decision in a outstanding local rivalry contest to win the European light-heavyweight championship.
The arena grew hushed for a profoundly moving homage before the fight as 10 bells tolled in memory of the city's native Hatton, who passed away 46 years old in September.
It was the first major televised fight night in the city since the passing of Hatton. As the concluding sound disappeared, the stillness gave way to a shout of "only one Hatton".
The competition during the bout equaled the emotion. Arthur was sent to the canvas by a powerful punch directly to the face in the second round, standing uncertainly to his footing on the referee's count.
But the Manchester United-red shorts of the fighter soon advanced again. From the other corner, the opponent - in rival City blue - was damaged quickly, noticeable damage developing under his orbital area as the duo traded punishing blows.
Rea, 27, connected with strong blows but the champion, thirty-four, responded in kind with powerful upward punches as the pace hardly diminished over twelve rounds.
The victor narrowly won the result with official scores of even score, narrow lead and 115-112, but the two athletes were persistent and courageous, all the qualities their idol Hatton stood for.
