UK light heavyweight Buatsi made a winning yet underwhelming beginning to life under fresh promotional backing with a unanimous decision over Zach Parker in the Manchester arena.
The Olympic bronze medallist's work rate seemingly secured him a majority decision in a competitive 10-round bout at the Co-op Live Arena.
But Parker found success, delivering effective individual punches in a contest where the techniques never quite clicked, with excessive holding spoiling the fight.
The officials scored it 96-94 to Buatsi, with the third a even score.
"It wasn't my greatest showing but what do champions do? They win," Buatsi commented in the arena as he was greeted with boos from the spectators.
The British fighter got back to winning after his first professional defeat - an thrilling contest with Callum Smith in February - to secure a twentieth professional win.
Some ringside observers believed Parker, 31, merited the win but the British boxer endured the second setback of his 28-bout career.
The Champion Earns Victory in Slow Match
Buatsi's progress has stalled in recent times through promotional disputes and long spells of lack of fights.
Once tipped as the next star of British boxing, he now stands trying to fulfil that early promise - maybe in what feels like a last chance - under new promotional backing.
He started carefully, with neither fighter ready to overcommit in a calculated opening few rounds.
Parker, whose sole prior loss came at the lower weight class against John Ryder in two years ago after damaging his hand during the bout, was making just his second bout at the higher weight class.
By the halfway stage, Parker had kept it close, creating difficulties for Buatsi, who operated with a protective stance to barely take the more effective periods.
The crowd's patience decreased because of constant clinching, with Parker going down various instances during close exchanges.
Parker closed well, but multiple periods were challenging to assess. Although, previous titleholder Carl Frampton - providing analysis for Dazn - had it particularly wide for the challenger, awarding Buatsi just one round.
The victor advances, but with the caliber of heavy hitter David Benavidez, and Russian champion Dmitry Bivol leading the category, the road to world glory - on this evidence - still appears challenging.
Hatton Tribute Inspires All-Manchester Contest
In the co-main event, Arthur beat Rea by close verdict in a terrific Manchester vs Manchester fight to secure the European light-heavyweight championship.
The arena grew hushed for a deeply poignant homage before the fight as a bell ceremony rang in honor of the city's native Ricky Hatton, who passed away 46 years old in September.
It was the first major televised fight night in the city since Hatton's death. As the final chime ended, the silence gave way to a chant of "only one Hatton".
The fighting within the ring matched the sentiment. Arthur was sent to the canvas by a powerful punch flush on the face in the early round, getting up unsteadily to his footing on the eight count.
But the Manchester United-red shorts of the fighter soon advanced again. From the other corner, Rea - in opposing blue - was marked up quickly, heavy swelling developing under his orbital area as the fighters exchanged punishing blows.
Rea, twenty-seven, landed power punches but the champion, thirty-four, responded in kind with powerful upward punches as the intensity seldom decreased over the full distance.
The victor narrowly won the result with scoring tallies of 114-114, narrow lead and 115-112, but the two athletes were relentless and full of heart, all the qualities their hero the legend stood for.
