UK light heavyweight Buatsi secured a victory yet underwhelming start to life under recent management with a points victory over Zach Parker in the Manchester arena.
The Olympic medal winner's punch output likely gained him a judges' verdict in a competitive 10-round contest at the Manchester venue.
But Parker had his moments, connecting with powerful individual punches in a contest where the styles didn't complement each other, with excessive holding spoiling the action.
The officials had it 96-94 to the winner, with the third a 95-95 draw.
"It wasn't my greatest performance but how do champions respond? They succeed," Buatsi stated in the ringside as he was greeted with disapproval from the audience.
The Londoner returned to winning ways after his maiden career setback - an epic battle with Callum Smith in last winter - to earn a 20th career victory.
Several boxing experts believed Parker, 31, deserved the decision but the Derbyshire fighter experienced the second setback of his 28-fight professional journey.
The Champion Earns Triumph in Dull Affair
His career development has stalled in the past few years through management issues and considerable time of inactivity.
Previously predicted as the rising talent of the British fight scene, he now finds himself trying to fulfil that early promise - possibly in what appears to be a last chance - under new promotional backing.
He opened tentatively, with both competitors prepared to be aggressive in a cagey opening few rounds.
Parker, whose only previous defeat came at super middleweight against his former opponent in two years ago after breaking his hand during the bout, was participating in his second appearance at light heavyweight.
By the halfway stage, Parker had kept it close, creating difficulties for Buatsi, who worked behind a solid defense to barely take the better periods.
The crowd's patience wore thin during constant clinching, with the challenger going down multiple occasions during close exchanges.
Parker finished the stronger, but multiple periods were challenging to assess. However, previous titleholder Carl Frampton - working with the broadcast network - had it strongly leaning for Parker, giving Buatsi just a single round.
Buatsi moves on, but with the presence of heavy hitter David Benavidez, and Russian star Bivol ruling the division, the journey to titles - judging by this showing - still appears challenging.
Hatton Memorial Motivates Manchester Derby Contest
In the supporting bout, Lyndon Arthur beat Rea by split-decision in a terrific Manchester vs Manchester contest to secure the European light-heavyweight title.
The arena fell silent for a deeply poignant homage prior to the bout as a bell ceremony sounded in honor of Manchester's own Hatton, who passed away aged 46 in last month.
It was the first major televised match card in the urban center since Hatton's passing. As the last bell ended, the stillness became a roar of "there's just one Hatton".
The fighting during the bout reflected the feeling. Arthur was knocked down by a powerful punch flush on the jaw in the second round, standing uncertainly to his feet on the eight count.
But the red-colored attire of Arthur soon advanced again. Across the ring, the opponent - in rival City blue - was injured soon, heavy swelling forming under his face as the fighters exchanged punishing blows.
Rea, twenty-seven, landed power punches but Arthur, thirty-four, matched the intensity with powerful upward punches as the pace hardly diminished over twelve rounds.
Arthur narrowly won the verdict with scoring tallies of even score, 115-113 and wider gap, but each competitor were persistent and courageous, all the qualities their idol Hatton embodied.
