British light heavyweight Buatsi secured a victory yet underwhelming start to life under new promoters with a decision win over Zach Parker in the Manchester arena.
The Olympic bronze medallist's work rate appeared to earn him a judges' verdict in a competitive 10-round bout at the Manchester venue.
But Parker found success, connecting with powerful individual punches in a match where the styles never quite clicked, with constant grabbing marring the fight.
The officials had it 96-94 to Buatsi, with the remaining official a 95-95 draw.
"It wasn't my greatest performance but what do champions do? They succeed," the victor commented in the arena as he was faced negative reactions from the audience.
The British fighter returned to winning ways after his first professional defeat - an epic battle with Callum Smith in February - to secure a 20th pro success.
Some ringside observers felt Parker, thirty-one, deserved the win but the Derbyshire fighter experienced the second loss of his 28-match professional journey.
The Champion Earns Victory in Uneventful Encounter
Buatsi's progress has slowed in recent years through promotional disputes and considerable time of lack of fights.
Previously predicted as the future of the British fight scene, he now stands trying to fulfil that early promise - perhaps in what appears to be a final roll of the dice - under recent support.
He opened tentatively, with neither fighter ready to overcommit in a cagey opening few rounds.
The challenger, whose single earlier setback came at super-middleweight against John Ryder in two years ago after suffering a hand injury during the bout, was making just his second fight at light-heavyweight.
By the middle rounds, Parker had kept it close, making life awkward for the favorite, who worked behind a solid defense to narrowly win the more effective rounds.
The crowd's patience diminished amid frequent holding, with the challenger slipping to the canvas multiple occasions during grappling.
Parker closed well, but many rounds were difficult to score. However, previous titleholder the boxing analyst - working with Dazn - had it significantly in favor for Parker, awarding Buatsi just one round.
The victor progresses, but with the caliber of power puncher David Benavidez, and Russian star Dmitry Bivol dominating the weight class, the path to championship success - on this evidence - still looks steep.
Hatton Homage Fuels All-Manchester Fight
In the secondary fight, Lyndon Arthur defeated Rea by split-decision in a excellent Manchester vs Manchester battle to capture the continental belt.
The venue fell silent for a profoundly moving homage ahead of the contest as a bell ceremony rang in honor of Manchester's own Ricky Hatton, who passed away 46 years old in September.
It was the initial significant broadcast boxing event in the urban center since Hatton's passing. As the concluding sound ended, the silence gave way to a chant of "there's just one Ricky Hatton".
The action during the bout reflected the sentiment. The eventual winner was sent to the canvas by a left hook squarely on the face in the initial stage, 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 marked up quickly, noticeable damage appearing under his face as the duo landed punishing blows.
Rea, 27, connected with strong blows but the champion, thirty-four, matched the intensity with effective uppercuts as the pace hardly diminished over twelve rounds.
The victor narrowly won the decision with official scores of even score, narrow lead and clearer margin, but the two athletes were persistent and brave, everything their idol the legend stood for.
