British light-heavyweight Buatsi made a winning yet disappointing beginning to life under fresh promotional backing with a points victory over Zach Parker in Manchester.
The Olympic medal winner's activity level appeared to earn him a judges' verdict in a competitive ten-round bout at the Manchester venue.
But Parker had his moments, delivering effective clean blows in a contest where the techniques never quite clicked, with frequent clinching spoiling the action.
Two judges had it 96-94 to Buatsi, with the final judge a even score.
"It wasn't my finest performance but how do champions respond? They succeed," the victor commented in the ring as he was greeted with boos from the crowd.
The Londoner got back to winning after his initial pro loss - an thrilling contest with his previous opponent in last winter - to secure a 20th career victory.
Several boxing experts felt the challenger, 31, should have been awarded the win but the contender experienced the second loss of his 28-match career.
The Champion Secures Triumph in Uneventful Match
The fighter's advancement has plateaued in recent years through promotional disputes and considerable time of lack of fights.
Previously predicted as the future of UK boxing, he now stands trying to fulfil that early promise - perhaps in what feels like a last chance - under new promotional backing.
He opened tentatively, with the two boxers willing to take risks in a calculated opening few rounds.
The challenger, whose single earlier setback came at super-middleweight against John Ryder in 2022 after suffering a hand injury in the contest, was participating in his second appearance at light heavyweight.
By the halfway stage, the underdog had kept it close, creating difficulties for the favorite, who operated with a solid defense to barely take the better periods.
The crowd's patience diminished because of frequent holding, with the challenger falling to the floor multiple occasions during clinches.
Parker closed well, but multiple periods were challenging to assess. However, ex-champion Carl Frampton - providing analysis for Dazn - had it strongly leaning for Parker, giving Buatsi just one round.
Buatsi progresses, but with the presence of power puncher David Benavidez, and Russian champion Dmitry Bivol dominating the weight class, the path to championship success - on this evidence - still seems difficult.
Hatton Tribute Motivates All-Manchester Battle
In the secondary fight, Lyndon Arthur defeated Bradley Rea by divided decision in a excellent all-Manchester battle to secure the European light heavyweight title.
The arena became quiet for a extremely emotional tribute before the fight as a bell ceremony sounded in memory of local hero Hatton, who succumbed at age 46 in last month.
It was the initial significant broadcast match card in the urban center since Hatton's death. As the last bell disappeared, the quiet became a roar of "there's just one Ricky Hatton".
The competition within the ring reflected the feeling. Arthur was knocked down by a significant blow directly to the face in the second round, getting up unsteadily to his footing on the referee's count.
But the red-colored shorts of the fighter soon came forward again. On the opposite side, the opponent - in opposing blue - was marked up quickly, significant bruising developing under his face as the fighters exchanged hard punches.
The challenger, 27, landed power punches but the champion, thirty-four, responded in kind with powerful upward punches as the pace seldom decreased over the full distance.
Arthur narrowly won the decision with scoring tallies of even score, close margin and 115-112, but both fighters were relentless and full of heart, all the qualities their inspiration Hatton stood for.
