UK light-heavyweight Buatsi made a winning yet disappointing start to his career under fresh promotional backing with a decision win over Zach Parker in the Manchester arena.
The Olympic bronze medallist's activity level appeared to earn him a majority decision in a close ten-round contest 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 excessive holding spoiling the fight.
Two judges had it 96-94 for to the winner, with the third a 95-95.
"It wasn't my best display but how do champions respond? They win," the victor commented in the ringside as he was greeted with boos from the spectators.
The British fighter got back to winning after his first professional defeat - an epic battle with Callum Smith in last winter - to claim a 20th pro success.
Several boxing experts believed the challenger, 31, should have been awarded the decision but the Derbyshire fighter endured the second loss of his 28-bout professional journey.
The Champion Claims Victory in Slow Encounter
Buatsi's progress has plateaued in recent years through contract problems and considerable time of inactivity.
Previously predicted as the rising talent of the British fight scene, he now stands trying to achieve expectations - maybe in what appears to be a final roll of the dice - under recent support.
He began cautiously, with the two boxers willing to be aggressive in a calculated initial rounds.
Parker, whose sole prior loss came at the lower weight class against John Ryder in 2022 after damaging his hand mid-fight, was participating in his second fight at light-heavyweight.
By the fight's midpoint, the underdog had stayed in contention, causing problems for Buatsi, who utilized a protective stance to narrowly win the cleaner rounds.
The spectators' acceptance diminished amid regular grabbing, with the challenger falling to the floor several times during grappling.
The underdog finished the stronger, but many rounds were difficult to score. Although, former world champion Carl Frampton - working with Dazn - had it significantly in favor for Parker, awarding Buatsi just one round.
The victor advances, but with the likes of power puncher David Benavidez, and Eastern European fighter Dmitry Bivol dominating the weight class, the road to world glory - judging by this showing - still appears challenging.
Ricky Hatton Memorial Fuels All-Manchester Battle
In the secondary fight, Lyndon Arthur overcame Rea by divided decision in a excellent Manchester vs Manchester fight to win the continental championship.
The stadium grew hushed for a extremely emotional homage ahead of the contest as ten bells sounded in honor of the city's native Ricky Hatton, who passed away at age 46 in last month.
It was the initial significant broadcast boxing event in the location since Hatton's death. As the concluding sound faded, the stillness transitioned to a shout of "there's only one Hatton".
The competition within the ring matched the feeling. Arthur was floored by a significant blow squarely on the face in the second round, standing uncertainly to his position on the count of eight.
But the red-colored shorts of the fighter soon advanced again. On the opposite side, Rea - in competitive blue - was marked up quickly, significant bruising developing under his orbital area as the pair landed powerful shots.
The challenger, 27, delivered effective strikes but Arthur, thirty-four, matched the intensity with powerful upward punches as the pace hardly diminished over the full distance.
The victor edged the decision with scoring tallies of draw, narrow lead and clearer margin, but the two athletes were determined and brave, exactly what their inspiration the legend embodied.
