UK light heavyweight Buatsi made a winning yet disappointing debut to life under new promoters with a decision win over Zach Parker in the Manchester arena.
The Olympic medal winner's punch output likely gained him a split decision in a tight ten-round fight at the Manchester venue.
But the challenger landed significant shots, landing some telling single shots in a contest where the styles didn't complement each other, with constant grabbing disrupting the action.
The officials had it 96-94 for to the winner, with the remaining official a 95-95.
"It wasn't my best display but what do champions do? They win," Buatsi stated in the arena as he was greeted with boos from the spectators.
The Londoner got back to winning after his first professional defeat - an memorable fight with his previous opponent in last winter - to claim a 20th pro success.
Several boxing experts thought the challenger, 31, should have been awarded the win but the contender experienced the second setback of his 28-bout career.
Buatsi Claims Triumph in Uneventful Encounter
His career development has stalled in the past few years through contract problems and extended periods of inactivity.
Earlier forecast as the future of the British fight scene, he now finds himself trying to fulfil that early promise - possibly in what appears to be a final roll of the dice - under new promotional backing.
He opened tentatively, with neither fighter ready to overcommit in a tentative initial rounds.
The challenger, whose single earlier setback came at the lower weight class against his former opponent in 2022 after suffering a hand injury during the bout, was competing in only his second appearance at light heavyweight.
By the middle rounds, the underdog had stayed in contention, creating difficulties for Buatsi, who utilized a tight guard to edge the better stanzas.
The crowd's patience diminished amid constant clinching, with Parker falling to the floor various instances during close exchanges.
Parker ended stronger, but many rounds were difficult to score. Although, previous titleholder Carl Frampton - working with the broadcast network - had it significantly in favor for the challenger, awarding Buatsi just only one stanza.
Buatsi moves on, but with the likes of hard hitter David Benavidez, and Russian champion Dmitry Bivol leading the category, the journey to titles - on this evidence - still looks steep.
Hatton Homage Fuels Manchester Derby Battle
In the secondary fight, Arthur overcame Rea by close verdict in a terrific Manchester vs Manchester contest to secure the European light heavyweight title.
The venue fell silent for a extremely emotional tribute ahead of the contest as ten bells tolled in remembrance of local hero Ricky Hatton, who died at age 46 in September.
It was the first major televised match card in the city since the passing of Hatton. As the final chime ended, the silence transitioned to a shout of "there's only one Hatton".
The competition during the bout equaled the sentiment. The eventual winner was sent to the canvas by a significant blow flush on the chin in the early round, getting up unsteadily to his feet on the count of eight.
But the red-colored shorts of the fighter soon pressed ahead again. On the opposite side, Rea - in opposing blue - was injured soon, heavy swelling forming under his face as the fighters traded hard punches.
Rea, 27, landed power punches but the champion, thirty-four, responded in kind with stinging uppercuts as the intensity hardly diminished over twelve rounds.
The victor edged the result with scoring tallies of 114-114, 115-113 and clearer margin, but the two athletes were persistent and full of heart, everything their idol Hatton stood for.
