UK light heavyweight Buatsi made a winning yet disappointing debut to life under fresh promotional backing with a points victory over Zach Parker in the Manchester arena.
The Olympic bronze medallist's work rate likely gained him a split decision in a competitive 10-round fight at the boxing arena.
But the challenger landed significant shots, landing some telling individual punches in a fight where the techniques never quite clicked, with constant grabbing disrupting the action.
Two judges judged it 96-94 to Buatsi, with the final judge a 95-95 draw.
"It wasn't my finest showing but how do champions respond? They prevail," Buatsi said in the ring as he was greeted with negative reactions from the audience.
The Londoner returned to winning ways after his initial pro loss - an memorable fight with Callum Smith in last winter - to claim a twentieth professional win.
Several boxing experts thought Parker, 31, merited the decision but the Derbyshire fighter suffered the second setback of his 28-fight career.
The Champion Earns Victory in Uneventful Encounter
His career development has stalled in recent times through promotional disputes and considerable time of lack of fights.
Once tipped as the rising talent of UK boxing, he now stands trying to fulfil that early promise - perhaps in what feels like a final roll of the dice - under fresh management.
He opened tentatively, with the two boxers willing to take risks in a calculated initial rounds.
The challenger, whose single earlier setback came at super-middleweight against his former opponent in 2022 after breaking his hand mid-fight, was making just his second appearance at the higher weight class.
By the halfway stage, the underdog had kept it close, causing problems for Buatsi, who worked behind a tight guard to narrowly win the more effective rounds.
The audience's tolerance wore thin during frequent holding, with Parker falling to the floor several times during grappling.
Parker finished the stronger, but many rounds were challenging to assess. Nevertheless, previous titleholder the boxing analyst - providing analysis for the broadcast network - had it strongly leaning for Parker, scoring for Buatsi just only one stanza.
Buatsi moves on, but with the caliber of heavy hitter David Benavidez, and Russian champion Dmitry Bivol dominating the weight class, the path to championship success - judging by this showing - still looks steep.
Ricky Hatton Memorial Fuels Manchester Derby Fight
In the secondary fight, Arthur beat Bradley Rea by split-decision in a terrific local rivalry contest to capture the continental championship.
The venue fell silent for a profoundly moving tribute before the fight as ten bells tolled in honor of the city's native Hatton, who died 46 years old in September.
It was the initial significant broadcast match card in the urban center since the passing of Hatton. As the final chime disappeared, the silence transitioned to a chant of "only one Ricky Hatton".
The fighting during the bout matched the feeling. Arthur was floored by a powerful punch squarely on the face in the initial stage, standing uncertainly to his position on the referee's count.
But the traditional red equipment of the fighter soon pressed ahead again. On the opposite side, Rea - in opposing blue - was marked up early, noticeable damage appearing under his orbital area as the pair exchanged powerful shots.
Rea, twenty-seven, landed power punches but the champion, 34, responded in kind with stinging uppercuts as the pace rarely dropped over twelve rounds.
The victor narrowly won the result with judges scorecards of even score, 115-113 and 115-112, but the two athletes were determined and brave, exactly what their inspiration the legend stood for.
