British light-heavyweight Buatsi earned a win yet unimpressive beginning to life under fresh promotional backing with a decision win over Zach Parker in Manchester.
The Olympic medal winner's work rate appeared to earn him a majority decision in a close 10-round fight at the boxing arena.
But the challenger had his moments, landing some telling clean blows in a match where the styles didn't complement each other, with constant grabbing disrupting the action.
Two judges judged it 96-94 to the winner, with the third a 95-95.
"It wasn't my finest display but what do champions do? They prevail," the victor commented in the ringside as he was faced disapproval from the crowd.
The British fighter got back to winning after his maiden career setback - an memorable fight with Callum Smith in February - to secure a twentieth professional win.
Several boxing experts thought Parker, thirty-one, deserved the decision but the Derbyshire fighter endured the second defeat of his 28-fight professional journey.
The Champion Earns Victory in Dull Affair
His career development has stalled in recent times through management issues and considerable time of inactivity.
Previously predicted as the future of British boxing, he now is positioned trying to achieve expectations - possibly in what feels like a last chance - under new promotional backing.
He began cautiously, with both competitors ready to overcommit in a calculated early stages.
Parker, whose single earlier setback came at the lower weight class against his former opponent in two years ago after breaking his hand mid-fight, was making just his second bout at light-heavyweight.
By the middle rounds, the underdog had stayed in contention, creating difficulties for the favorite, who utilized a solid defense to barely take the cleaner stanzas.
The crowd's patience diminished during constant clinching, with Parker falling to the floor several times during clinches.
Parker closed well, but multiple periods were difficult to score. Nevertheless, former world champion Carl Frampton - commentating on the broadcast network - had it significantly in favor for Parker, giving Buatsi just only one stanza.
The victor moves on, but with the caliber of heavy hitter David Benavidez, and Russian star Bivol leading the category, the path to championship success - judging by this showing - still looks steep.
Hatton Homage Fuels All-Manchester Battle
In the co-main event, Lyndon Arthur overcame Rea by close verdict in a terrific all-Manchester fight to capture the continental championship.
The stadium fell silent for a profoundly moving tribute ahead of the contest as ten bells rang in honor of local hero Hatton, who succumbed 46 years old in September.
It was the premier televised match card in the urban center since the passing of Hatton. As the last bell ended, the quiet transitioned to a chant of "there's just one Ricky Hatton".
The action within the ring matched the emotion. Arthur was knocked down by a powerful punch directly to the jaw in the initial stage, getting up unsteadily to his footing on the eight count.
But the Manchester United-red attire of the fighter soon advanced again. Across the ring, Rea - in rival City blue - was marked up soon, significant bruising forming under his face as the fighters traded hard punches.
The challenger, 27, landed power punches but the champion, 34, responded in kind with effective uppercuts as the pace rarely dropped over 12 rounds.
The victor edged the verdict with official scores of even score, narrow lead and 115-112, but both fighters were relentless and full of heart, exactly what their idol Hatton represented.
