British light heavyweight Buatsi secured a victory yet disappointing start to life under recent management with a unanimous decision over Zach Parker in Manchester.
The Olympic medal winner's punch output seemingly secured him a majority decision in a tight 10-round bout at the Manchester venue.
But Parker found success, connecting with powerful individual punches in a fight where the techniques never quite clicked, with constant grabbing marring the fight.
The officials scored it 96-94 to the winner, with the remaining official a 95-95 draw.
"It wasn't my finest showing but what defines champions? They win," the victor stated in the arena as he was met by negative reactions from the audience.
The British fighter got back to winning after his maiden career setback - an epic battle with Callum Smith in February - to secure a 20th career victory.
Several boxing experts believed the challenger, thirty-one, should have been awarded the win but the Derbyshire fighter suffered the second loss of his 28-fight career.
Buatsi Secures Victory in Slow Affair
The fighter's advancement has slowed in recent times through promotional disputes and extended periods of inactivity.
Previously predicted as the rising talent of UK boxing, he now finds himself trying to realize his potential - perhaps in what feels like a last chance - under new promotional backing.
He started carefully, with the two boxers willing to be aggressive in a cagey opening few rounds.
The challenger, whose only previous defeat came at super middleweight against his former opponent in two years ago after breaking his hand mid-fight, was participating in his second appearance at light-heavyweight.
By the middle rounds, Parker had kept it close, making life awkward for Buatsi, who utilized a tight guard to barely take the more effective periods.
The crowd's patience diminished during regular grabbing, with Parker slipping to the canvas several times during clinches.
Parker finished the stronger, but many rounds were difficult to score. However, previous titleholder the boxing analyst - commentating on the broadcast network - had it particularly wide for Parker, scoring for Buatsi just a single round.
Buatsi moves on, but with the likes of power puncher Benavidez, and Russian champion Dmitry Bivol ruling the division, the path to championship success - based on this performance - still seems difficult.
Hatton Memorial Inspires All-Manchester Contest
In the co-main event, Lyndon Arthur defeated Bradley Rea by split-decision in a outstanding all-Manchester contest to secure the European light heavyweight championship.
The stadium fell silent for a profoundly moving memorial ahead of the contest as a bell ceremony tolled in memory of Manchester's own Hatton, who succumbed aged 46 in last month.
It was the initial significant broadcast match card in the location since Hatton's death. As the final chime ended, the quiet transitioned to a roar of "there's just one Hatton".
The action inside the ropes equaled the feeling. The eventual winner was knocked down by a significant blow flush on the chin in the initial stage, standing uncertainly to his position on the eight count.
But the traditional red attire of Arthur soon came forward again. From the other corner, the opponent - in opposing blue - was injured early, significant bruising developing under his orbital area as the pair traded hard punches.
Rea, twenty-seven, landed power punches but Arthur, thirty-four, matched the intensity with effective uppercuts as the action hardly diminished over twelve rounds.
The victor narrowly won the verdict with official scores of even score, close margin and wider gap, but both fighters were determined and full of heart, all the qualities their idol Hatton represented.
