British light-heavyweight Buatsi secured a victory yet disappointing start to life under fresh promotional backing with a unanimous decision over Zach Parker in the Manchester arena.
The Olympic medal winner's work rate seemingly secured him a split decision in a competitive 10-round contest at the boxing arena.
But Parker found success, delivering effective individual punches in a contest where the approaches never quite clicked, with constant grabbing spoiling the contest.
Two judges had it 96-94 for to Buatsi, with the remaining official a 95-95.
"It wasn't my greatest showing but how do champions respond? They succeed," Buatsi said in the ringside as he was met by negative reactions from the crowd.
The Londoner got back to winning after his first professional defeat - an epic battle with Callum Smith in last winter - to claim a 20th career victory.
Some ringside observers felt Parker, 31, should have been awarded the decision but the Derbyshire fighter endured the second defeat of his 28-match career.
Buatsi Claims Win in Dull Affair
The fighter's advancement has stalled in the past few years through promotional disputes and long spells of lack of fights.
Earlier forecast as the future of the British fight scene, he now is positioned trying to realize his potential - possibly in what feels like a last chance - under recent support.
He began cautiously, with the two boxers prepared to be aggressive in a tentative opening few rounds.
Parker, whose single earlier setback came at the lower weight class against John Ryder in 2022 after suffering a hand injury during the bout, was making just his second bout at the higher weight class.
By the middle rounds, Parker had made it competitive, creating difficulties for the favorite, who operated with a tight guard to edge the better periods.
The spectators' acceptance wore thin amid regular grabbing, with Parker going down multiple occasions during grappling.
The underdog ended stronger, but many rounds were challenging to assess. However, previous titleholder Carl Frampton - providing analysis for Dazn - had it particularly wide for Parker, scoring for Buatsi just only one stanza.
The victor progresses, but with the presence of heavy hitter David Benavidez, and Russian champion Bivol ruling the division, the journey to titles - on this evidence - still looks steep.
Ricky Hatton Homage Motivates All-Manchester Contest
In the co-main event, Arthur overcame Bradley Rea by divided decision in a excellent Manchester vs Manchester contest to secure the European light-heavyweight championship.
The arena grew hushed for a deeply poignant homage ahead of the contest as 10 bells sounded in honor of local hero Ricky Hatton, who died at age 46 in September.
It was the initial significant broadcast boxing event in the urban center since Hatton's death. As the final chime ended, the silence transitioned to a shout of "there's just one Hatton".
The action within the ring reflected the sentiment. Arthur was knocked down by a significant blow flush on the chin in the initial stage, standing uncertainly to his footing on the count of eight.
But the red-colored equipment of Arthur soon advanced again. Across the ring, Rea - in opposing blue - was damaged soon, significant bruising appearing under his eye as the fighters landed hard punches.
The challenger, twenty-seven, landed power punches but the champion, thirty-four, responded in kind with stinging uppercuts as the action seldom decreased over twelve rounds.
Arthur barely secured the verdict with judges scorecards of draw, 115-113 and wider gap, but each competitor were persistent and courageous, exactly what their inspiration Hatton represented.
