UK light heavyweight Buatsi earned a win yet disappointing start to his career under recent management with a decision win over Zach Parker in Manchester.
The Olympic bronze medallist's activity level appeared to earn him a majority decision in a tight ten-round fight at the boxing arena.
But Parker had his moments, connecting with powerful individual punches in a match where the techniques failed to mesh, with constant grabbing spoiling the action.
The scoring judges judged it 96-94 to the winner, with the third a 95-95 draw.
"It wasn't my finest performance but what do champions do? They win," the victor said in the arena as he was greeted with negative reactions from the crowd.
The British fighter got back to winning after his initial pro loss - an epic battle with his previous opponent in last winter - to earn a 20th pro success.
Some ringside observers thought the challenger, 31, deserved the win but the Derbyshire fighter experienced the second setback of his 28-fight career.
The Champion Earns Win in Uneventful Match
Buatsi's progress has stalled in recent years through contract problems and considerable time of inactivity.
Earlier forecast as the rising talent of the British fight scene, he now finds himself trying to achieve expectations - maybe in what feels like a final roll of the dice - under fresh management.
He began cautiously, with neither fighter prepared to take risks in a calculated early stages.
The challenger, whose sole prior loss came at the lower weight class against his former opponent in two years ago after suffering a hand injury mid-fight, was competing in only his second fight at light-heavyweight.
By the fight's midpoint, the underdog had made it competitive, causing problems for the favorite, who worked behind a protective stance to edge the better periods.
The audience's tolerance diminished amid frequent holding, with Parker falling to the floor several times during clinches.
Parker closed well, but multiple periods were challenging to assess. However, ex-champion the boxing analyst - commentating on the broadcast network - had it particularly wide for the challenger, giving Buatsi just a single round.
Buatsi moves on, but with the likes of heavy hitter David Benavidez, and Russian star Bivol dominating the weight class, the journey to titles - judging by this showing - still seems difficult.
Ricky Hatton Homage Inspires All-Manchester Battle
In the supporting bout, Arthur overcame Bradley Rea by close verdict in a excellent local rivalry fight to win the continental belt.
The arena grew hushed for a profoundly moving tribute before the fight as a bell ceremony rang in honor of local hero Hatton, who passed away 46 years old in last month.
It was the premier televised fight night in the city since Hatton's passing. As the last bell faded, the quiet transitioned to a roar of "there's just one Ricky Hatton".
The action during the bout matched the feeling. Arthur was floored by a left hook flush on the face in the early round, rising shakily to his position on the eight count.
But the red-colored attire of the fighter soon came forward again. On the opposite side, Rea - in opposing blue - was marked up quickly, noticeable damage forming under his orbital area as the duo exchanged hard punches.
The challenger, 27, connected with strong blows but the champion, thirty-four, responded in kind with stinging uppercuts as the pace rarely dropped over the full distance.
Arthur narrowly won the verdict with judges scorecards of draw, close margin and clearer margin, but both fighters were determined and courageous, everything their inspiration the legend embodied.
