British light-heavyweight Buatsi made a winning yet unimpressive debut to his career under recent management with a decision win over Zach Parker in Manchester.
The Olympic medal winner's punch output seemingly secured him a split decision in a competitive 10-round fight at the Manchester venue.
But the challenger found success, delivering effective single shots in a contest where the styles didn't complement each other, with constant grabbing spoiling the fight.
Two judges judged it 96-94 in favor to Buatsi, with the third a even score.
"It wasn't my greatest showing but what defines champions? They win," Buatsi said in the ringside as he was greeted with negative reactions from the spectators.
The British fighter returned to winning ways after his first professional defeat - an memorable fight with Callum Smith in February - to claim a 20th pro success.
Several boxing experts thought the challenger, 31, should have been awarded the decision but the British boxer suffered the second defeat of his 28-bout professional journey.
The Champion Claims Win in Dull Match
His career development has slowed in the past few years through promotional disputes and extended periods of inactivity.
Once tipped as the rising talent of the British fight scene, he now stands trying to achieve expectations - perhaps in what seems like a last chance - under recent support.
He opened tentatively, with both competitors prepared to overcommit in a calculated early stages.
The challenger, whose single earlier setback came at the lower weight class against his former opponent in two years ago after damaging his hand during the bout, was competing in only his second bout at light-heavyweight.
By the fight's midpoint, Parker had made it competitive, causing problems for the favorite, who utilized a protective stance to narrowly win the more effective periods.
The spectators' acceptance diminished because of regular grabbing, with the challenger falling to the floor multiple occasions during clinches.
Parker finished the stronger, but multiple periods were hard to judge. Nevertheless, previous titleholder Carl Frampton - providing analysis for Dazn - had it strongly leaning for the challenger, giving Buatsi just only one stanza.
The victor advances, but with the likes of power puncher David Benavidez, and Russian champion Dmitry Bivol ruling the division, the journey to titles - based on this performance - still looks steep.
Hatton Tribute Fuels Local Rivalry Fight
In the secondary fight, Lyndon Arthur defeated Bradley Rea by divided decision in a outstanding Manchester vs Manchester contest to secure the European light heavyweight belt.
The stadium fell silent for a profoundly moving memorial prior to the bout as ten bells rang in honor of local hero Ricky Hatton, who succumbed 46 years old in September.
It was the initial significant broadcast fight night in the urban center since Hatton's death. As the concluding sound ended, the quiet gave way to a roar of "there's just one Hatton".
The fighting inside the ropes equaled the sentiment. Arthur was floored by a significant blow squarely on the jaw in the initial stage, standing uncertainly to his feet on the eight count.
But the red-colored attire of Arthur soon advanced again. Across the ring, Rea - in rival City blue - was injured quickly, noticeable damage forming under his eye as the fighters traded hard punches.
Rea, twenty-seven, connected with strong blows but the champion, thirty-four, responded in kind with powerful upward punches as the action rarely dropped over twelve rounds.
The victor edged the verdict with scoring tallies of draw, 115-113 and clearer margin, but both fighters were relentless and full of heart, exactly what their idol Hatton represented.
