UK light-heavyweight Buatsi made a winning yet disappointing start to his career under recent management with a points victory over Zach Parker in Manchester.
The Olympic medal winner's activity level seemingly secured him a majority decision in a close 10-round fight at the Co-op Live Arena.
But Parker found success, delivering effective individual punches in a fight where the styles didn't complement each other, with constant grabbing disrupting the fight.
Two judges scored it 96-94 to the winner, with the final judge a 95-95 draw.
"It wasn't my best performance but what defines champions? They prevail," Buatsi commented in the ringside as he was faced disapproval from the audience.
The British fighter bounced back after his maiden career setback - an memorable fight with his previous opponent in February - to claim a twentieth professional win.
Some ringside observers felt the challenger, thirty-one, should have been awarded the win but the contender experienced the second defeat of his 28-fight professional journey.
The Champion Secures Victory in Dull Affair
His career development has plateaued in recent years through contract problems and extended periods of inactivity.
Once tipped as the next star of UK boxing, he now is positioned trying to fulfil that early promise - perhaps in what appears to be a last chance - under fresh management.
He opened tentatively, with neither fighter willing to take risks in a calculated early stages.
Parker, whose sole prior loss came at the lower weight class against John Ryder in two years ago after suffering a hand injury during the bout, was competing in only his second fight at light heavyweight.
By the middle rounds, the underdog had stayed in contention, making life awkward for Buatsi, who utilized a tight guard to barely take the better periods.
The crowd's patience diminished because of regular grabbing, with Parker going down various instances during clinches.
Parker closed well, but multiple periods were difficult to score. Nevertheless, previous titleholder Carl Frampton - working with Dazn - had it significantly in favor for Parker, giving Buatsi just a single round.
The victor 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 - judging by this showing - still seems difficult.
Hatton Tribute Inspires Local Rivalry Contest
In the co-main event, Lyndon Arthur overcame Bradley Rea by close verdict in a excellent local rivalry battle to capture the continental belt.
The venue grew hushed for a extremely emotional homage prior to the bout as a bell ceremony tolled in memory of Manchester's own Ricky Hatton, who passed away aged 46 in last month.
It was the first major televised boxing event in the urban center since Hatton's death. As the concluding sound disappeared, the silence transitioned to a roar of "only one Hatton".
The action within the ring equaled the feeling. The eventual winner was sent to the canvas by a left hook squarely on the jaw in the early round, rising shakily to his footing on the count of eight.
But the Manchester United-red equipment of the fighter soon advanced again. On the opposite side, Rea - in competitive blue - was injured quickly, significant bruising appearing under his eye as the duo landed punishing blows.
The challenger, twenty-seven, delivered effective strikes but Arthur, thirty-four, fought fire with fire with effective uppercuts as the pace hardly diminished over twelve rounds.
The victor edged the verdict with official scores of draw, 115-113 and clearer margin, but the two athletes were determined and brave, everything their idol the legend represented.
