UK light-heavyweight Buatsi secured a victory yet disappointing start to his career under new promoters with a decision win over Zach Parker in the Manchester arena.
The Olympic bronze medallist's activity level likely gained him a split decision in a competitive ten-round bout at the Co-op Live Arena.
But Parker landed significant shots, delivering effective clean blows in a match where the styles didn't complement each other, with excessive holding marring the action.
Two judges scored it 96-94 for to the winner, with the final judge a 95-95.
"It wasn't my greatest showing but what defines champions? They succeed," the victor commented in the ringside as he was greeted with disapproval from the spectators.
The Londoner bounced back after his maiden career setback - an memorable fight with his previous opponent in last winter - to claim a 20th career victory.
Several boxing experts believed Parker, 31, deserved the decision but the contender suffered the second defeat of his 28-match professional journey.
The Champion Earns Win in Dull Affair
Buatsi's progress has stalled in recent years through promotional disputes and extended periods of lack of fights.
Once tipped as the future of British boxing, he now stands trying to achieve expectations - perhaps in what feels like a final roll of the dice - under fresh management.
He started carefully, with neither fighter ready to be aggressive in a calculated opening few rounds.
The challenger, whose single earlier setback came at the lower weight class against John Ryder in 2022 after suffering a hand injury in the contest, was competing in only his second appearance at light-heavyweight.
By the fight's midpoint, the underdog had stayed in contention, making life awkward for the favorite, who worked behind a protective stance to barely take the cleaner periods.
The crowd's patience decreased amid regular grabbing, with the challenger slipping to the canvas various instances during clinches.
Parker ended stronger, but many rounds were difficult to score. However, previous titleholder the boxing analyst - providing analysis for the broadcast network - had it significantly in favor for the challenger, awarding Buatsi just one round.
The victor moves on, but with the likes of power puncher Benavidez, and Eastern European fighter Dmitry Bivol ruling the division, the path to championship success - judging by this showing - still appears challenging.
Ricky Hatton Homage Inspires Manchester Derby Battle
In the secondary fight, Arthur defeated Bradley Rea by split-decision in a outstanding all-Manchester fight to secure the European light heavyweight championship.
The venue fell silent for a deeply poignant memorial before the fight as 10 bells tolled in memory of Manchester's own Hatton, who passed away aged 46 in last month.
It was the premier televised match card in the urban center since the passing of Hatton. As the last bell ended, the quiet gave way to a roar of "there's just one Hatton".
The action inside the ropes equaled the sentiment. The eventual winner was knocked down by a left hook directly to the face in the early round, rising shakily to his footing on the referee's count.
But the red-colored equipment of the fighter soon advanced again. From the other corner, the opponent - in rival City blue - was marked up soon, noticeable damage forming under his orbital area as the duo landed powerful shots.
The challenger, twenty-seven, connected with strong blows but Arthur, 34, responded in kind with stinging uppercuts as the intensity seldom decreased over the full distance.
The victor edged the verdict with official scores of even score, close margin and wider gap, but the two athletes were relentless and courageous, all the qualities their inspiration the legend represented.
