UK light-heavyweight Buatsi earned a win yet underwhelming debut to life under fresh promotional backing with a points victory over Zach Parker in Manchester.
The Olympic medal winner's punch output likely gained him a split decision in a competitive 10-round bout at the boxing arena.
But the challenger found success, connecting with powerful clean blows in a contest where the styles failed to mesh, with excessive holding spoiling the contest.
The officials had it 96-94 in favor to Buatsi, with the final judge a 95-95 draw.
"It wasn't my greatest showing but what defines champions? They win," the victor commented in the arena as he was met by negative reactions from the crowd.
The Londoner returned to winning ways after his first professional defeat - an thrilling contest with Callum Smith in February - to claim a 20th pro success.
Various analysts felt Parker, thirty-one, deserved the victory but the contender suffered the second defeat of his 28-match professional journey.
The Champion Earns Triumph in Dull Affair
Buatsi's progress has slowed in recent years through management issues and extended periods of lack of fights.
Earlier forecast as the rising talent of the British fight scene, he now finds himself trying to fulfil that early promise - perhaps in what seems like a ultimate opportunity - under recent support.
He started carefully, with neither fighter prepared to take risks in a tentative opening few rounds.
The challenger, whose sole prior loss came at the lower weight class against his former opponent in 2022 after damaging his hand in the contest, was competing in only his second bout at light-heavyweight.
By the middle rounds, the underdog had stayed in contention, causing problems for the favorite, who utilized a tight guard to barely take the cleaner stanzas.
The crowd's patience wore thin because of constant clinching, with the challenger going down various instances during clinches.
Parker ended stronger, but multiple periods were challenging to assess. However, former world champion Carl Frampton - providing analysis for Dazn - had it significantly in favor for the challenger, awarding Buatsi just a single round.
The victor progresses, but with the presence of hard hitter Benavidez, and Russian star Dmitry Bivol dominating the weight class, the path to championship success - judging by this showing - still looks steep.
Ricky Hatton Memorial Inspires All-Manchester Contest
In the co-main event, Arthur defeated Bradley Rea by divided decision in a terrific local rivalry battle to capture the European light heavyweight belt.
The arena grew hushed for a deeply poignant memorial before the fight as ten bells tolled in honor of local hero Ricky Hatton, who succumbed 46 years old in September.
It was the first major televised boxing event in the urban center since Hatton's death. As the last bell faded, the stillness became a shout of "only one Hatton".
The competition during the bout equaled the feeling. The eventual winner was sent to the canvas by a powerful punch squarely on the chin in the initial stage, getting up unsteadily to his position on the eight count.
But the traditional red equipment of Arthur soon advanced again. Across the ring, Rea - in opposing blue - was marked up quickly, heavy swelling forming under his face as the duo exchanged punishing blows.
The challenger, 27, landed power punches but the champion, thirty-four, matched the intensity with stinging uppercuts as the intensity seldom decreased over twelve rounds.
Arthur barely secured the result with judges scorecards of even score, close margin and 115-112, but the two athletes were relentless and brave, everything their hero Hatton embodied.
