British light heavyweight Buatsi earned a win yet unimpressive beginning to his career under fresh promotional backing with a decision win over Zach Parker in Manchester.
The Olympic bronze medallist's work rate appeared to earn him a majority decision in a competitive 10-round bout at the Manchester venue.
But the challenger landed significant shots, landing some telling single shots in a fight where the techniques failed to mesh, with excessive holding marring the fight.
The officials judged it 96-94 to the winner, with the final judge a even score.
"It wasn't my finest performance but how do champions respond? They win," the victor commented in the ring as he was greeted with disapproval from the crowd.
The Londoner returned to winning ways after his maiden career setback - an epic battle with Callum Smith in last winter - to secure a 20th career victory.
Several boxing experts felt the challenger, thirty-one, deserved the decision but the contender experienced the second setback of his 28-bout professional journey.
The Champion Secures Win in Uneventful Affair
The fighter's advancement has plateaued in recent times through promotional disputes and long spells of inactivity.
Earlier forecast as the next star of British boxing, he now is positioned trying to fulfil that early promise - perhaps in what feels like a last chance - under fresh management.
He started carefully, with both competitors prepared to take risks in a tentative initial rounds.
The challenger, whose only previous defeat came at super-middleweight against John Ryder in 2022 after damaging his hand during the bout, was making just his second bout at light-heavyweight.
By the halfway stage, the underdog had kept it close, causing problems for the favorite, who utilized a protective stance to narrowly win the cleaner rounds.
The audience's tolerance wore thin during frequent holding, with the challenger falling to the floor various instances during grappling.
The underdog ended stronger, but several stanzas were difficult to score. However, ex-champion Carl Frampton - providing analysis for the broadcast network - had it strongly leaning for the challenger, giving Buatsi just a single round.
Buatsi progresses, but with the presence of hard hitter David Benavidez, and Russian star Dmitry Bivol dominating the weight class, the road to world glory - based on this performance - still seems difficult.
Hatton Homage Motivates Manchester Derby Contest
In the supporting bout, Arthur overcame Rea by close verdict in a excellent local rivalry contest to secure the European light-heavyweight championship.
The venue fell silent for a profoundly moving tribute prior to the bout as ten bells sounded in memory of Manchester's own Ricky Hatton, who succumbed aged 46 in September.
It was the first major televised match card in the urban center since the passing of Hatton. As the final chime disappeared, the quiet transitioned to a shout of "there's just one Hatton".
The fighting inside the ropes equaled the sentiment. The eventual winner was floored by a significant blow directly to the face in the early round, standing uncertainly to his position on the referee's count.
But the traditional red shorts of the fighter soon advanced again. Across the ring, Rea - in rival City blue - was injured soon, significant bruising developing under his orbital area as the duo exchanged powerful shots.
Rea, 27, connected with strong blows but the champion, thirty-four, matched the intensity with powerful upward punches as the pace hardly diminished over twelve rounds.
The victor barely secured the result with judges scorecards of even score, narrow lead and 115-112, but both fighters were persistent and courageous, exactly what their hero Hatton stood for.
