British light-heavyweight Buatsi earned a win yet underwhelming debut to his career under new promoters with a unanimous decision over Zach Parker in Manchester.
The Olympic medal winner's punch output seemingly secured him a majority decision in a competitive 10-round fight at the Co-op Live Arena.
But the challenger had his moments, landing some telling individual punches in a fight where the approaches failed to mesh, with frequent clinching spoiling the action.
The scoring judges scored it 96-94 in favor to Buatsi, with the final judge a even score.
"It wasn't my greatest display but what do champions do? They win," Buatsi commented in the arena as he was greeted with disapproval from the audience.
The Londoner returned to winning ways after his first professional defeat - an thrilling contest with Callum Smith in last winter - to secure a twentieth professional win.
Several boxing experts believed the challenger, thirty-one, should have been awarded the victory but the Derbyshire fighter endured the second defeat of his 28-fight professional journey.
The Champion Claims Victory in Uneventful Encounter
The fighter's advancement has stalled in the past few years through contract problems and considerable time of inactivity.
Previously predicted as the next star of British boxing, he now stands trying to achieve expectations - perhaps in what feels like a final roll of the dice - under new promotional backing.
He opened tentatively, with the two boxers prepared to overcommit in a calculated opening few rounds.
The challenger, whose single earlier setback came at super middleweight against his former opponent in two years ago after damaging his hand during the bout, was participating in his second fight at light heavyweight.
By the fight's midpoint, the underdog had stayed in contention, making life awkward for the favorite, who worked behind a tight guard to edge the cleaner rounds.
The audience's tolerance wore thin amid frequent holding, with the challenger slipping to the canvas multiple occasions during grappling.
The underdog closed well, but several stanzas were difficult to score. However, previous titleholder Carl Frampton - commentating on Dazn - had it particularly wide for the challenger, awarding Buatsi just one round.
Buatsi advances, but with the caliber of power puncher David Benavidez, and Russian star Dmitry Bivol leading the category, the journey to titles - judging by this showing - still appears challenging.
Ricky Hatton Memorial Inspires Local Rivalry Fight
In the supporting bout, Lyndon Arthur overcame Rea by close verdict in a terrific all-Manchester fight to secure the continental belt.
The arena grew hushed for a deeply poignant homage before the fight as ten bells rang in honor of Manchester's own Hatton, who died aged 46 in recently.
It was the initial significant broadcast match card in the urban center since Hatton's death. As the final chime disappeared, the stillness gave way to a shout of "only one Hatton".
The competition during the bout equaled the feeling. Arthur was sent to the canvas by a significant blow directly to the jaw in the second round, standing uncertainly to his footing on the referee's count.
But the red-colored equipment of the fighter soon pressed ahead again. On the opposite side, Rea - in competitive blue - was marked up quickly, heavy swelling forming under his orbital area as the pair exchanged hard punches.
The challenger, twenty-seven, landed power punches but Arthur, thirty-four, responded in kind with powerful upward punches as the action rarely dropped over 12 rounds.
Arthur barely secured the result with judges scorecards of even score, 115-113 and clearer margin, but both fighters were persistent and brave, all the qualities their idol the legend represented.
