British light-heavyweight Buatsi made a winning yet unimpressive beginning to his career under new promoters with a unanimous decision over Zach Parker in Manchester.
The Olympic medal winner's activity level seemingly secured him a majority decision in a competitive 10-round bout at the boxing arena.
But Parker had his moments, connecting with powerful single shots in a contest where the styles never quite clicked, with constant grabbing spoiling the fight.
Two judges scored it 96-94 in favor to Buatsi, with the remaining official a 95-95.
"It wasn't my greatest showing but what do champions do? They prevail," Buatsi stated in the ring as he was faced boos from the crowd.
The Londoner returned to winning ways after his initial pro loss - an memorable fight with Callum Smith in last winter - to earn a 20th pro success.
Various analysts felt the challenger, 31, deserved the win but the British boxer endured the second defeat of his 28-fight career.
Buatsi Claims Triumph in Slow Encounter
The fighter's advancement has stalled in recent times through promotional disputes and considerable time of inactivity.
Previously predicted as the next star of the British fight scene, he now finds himself trying to achieve expectations - maybe in what feels like a last chance - under new promotional backing.
He began cautiously, with the two boxers prepared to be aggressive in a calculated early stages.
The challenger, whose only previous defeat came at super-middleweight against his former opponent in 2022 after suffering a hand injury during the bout, was participating in his second fight at light-heavyweight.
By the middle rounds, Parker had made it competitive, making life awkward for the favorite, who utilized a protective stance to edge the cleaner rounds.
The crowd's patience diminished because of frequent holding, with the challenger slipping to the canvas several times during grappling.
The underdog closed well, but many rounds were challenging to assess. However, former world champion Carl Frampton - working with the broadcast network - had it significantly in favor for Parker, giving Buatsi just only one stanza.
The victor advances, but with the caliber of hard hitter David Benavidez, and Russian champion Dmitry Bivol leading the category, the path to championship success - on this evidence - still appears challenging.
Ricky Hatton Memorial Inspires Local Rivalry Contest
In the co-main event, Arthur defeated Bradley Rea by split-decision in a outstanding all-Manchester fight to secure the European light heavyweight title.
The arena grew hushed for a profoundly moving tribute prior to the bout as 10 bells rang in honor of Manchester's own Ricky Hatton, who died at age 46 in last month.
It was the initial significant broadcast boxing event in the urban center since the passing of Hatton. As the final chime faded, the silence gave way to a shout of "only one Hatton".
The competition inside the ropes reflected the emotion. Arthur was floored by a significant blow directly to the face in the early round, rising shakily to his position on the count of eight.
But the traditional red equipment of Arthur soon pressed ahead again. On the opposite side, Rea - in rival City blue - was damaged early, significant bruising forming under his orbital area as the fighters landed hard punches.
The challenger, twenty-seven, delivered effective strikes but Arthur, 34, matched the intensity with stinging uppercuts as the pace hardly diminished over twelve rounds.
Arthur narrowly won the verdict with scoring tallies of even score, close margin and wider gap, but the two athletes were relentless and full of heart, everything their hero the legend embodied.
