UK light-heavyweight Buatsi earned a win yet underwhelming debut to his career under recent management with a unanimous decision over Zach Parker in Manchester.
The Olympic bronze medallist's activity level appeared to earn him a split decision in a tight ten-round contest at the boxing arena.
But Parker found success, landing some telling clean blows in a fight where the styles didn't complement each other, with excessive holding disrupting the contest.
The scoring judges judged it 96-94 to the winner, with the remaining official a 95-95 draw.
"It wasn't my greatest showing but what do champions do? They succeed," the victor stated in the ring as he was met by disapproval from the audience.
The Londoner bounced back after his maiden career setback - an epic battle with his previous opponent in February - to claim a 20th career victory.
Various analysts felt Parker, 31, merited the decision but the contender experienced the second loss of his 28-match career.
The Champion Secures Victory in Slow Match
Buatsi's progress has slowed in the past few years through promotional disputes and extended periods of inactivity.
Previously predicted as the future of British boxing, he now finds himself trying to fulfil that early promise - perhaps in what feels like a final roll of the dice - under new promotional backing.
He started carefully, with the two boxers ready to overcommit in a calculated opening few rounds.
The challenger, whose sole prior loss came at super middleweight against his former opponent in two years ago 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 utilized a solid defense to barely take the cleaner periods.
The audience's tolerance decreased during frequent holding, with the challenger going down several times during clinches.
Parker finished the stronger, but several stanzas were hard to judge. Nevertheless, ex-champion the boxing analyst - commentating on Dazn - had it strongly leaning for the challenger, scoring for Buatsi just only one stanza.
Buatsi moves on, but with the likes of heavy hitter David Benavidez, and Eastern European fighter Dmitry Bivol dominating the weight class, the road to world glory - based on this performance - still looks steep.
Ricky Hatton Tribute Inspires All-Manchester Fight
In the secondary fight, Lyndon Arthur overcame Bradley Rea by close verdict in a excellent local rivalry contest to capture the continental title.
The arena grew hushed for a deeply poignant tribute ahead of the contest as ten bells rang in remembrance of local hero Ricky Hatton, who succumbed at age 46 in last month.
It was the first major televised match card in the city since Hatton's death. As the concluding sound faded, the quiet gave way to a chant of "there's only one Ricky Hatton".
The fighting during the bout matched the emotion. The eventual winner was sent to the canvas by a left hook flush on the face in the second round, rising shakily to his position on the count of eight.
But the Manchester United-red equipment of the fighter soon advanced again. On the opposite side, the opponent - in rival City blue - was injured quickly, noticeable damage developing under his face as the fighters landed powerful shots.
The challenger, twenty-seven, connected with strong blows but Arthur, thirty-four, matched the intensity with effective uppercuts as the intensity rarely dropped over the full distance.
The victor barely secured the decision with scoring tallies of even score, narrow lead and wider gap, but each competitor were determined and full of heart, all the qualities their inspiration the legend represented.
