UK light-heavyweight Buatsi earned a win yet disappointing beginning to life under fresh promotional backing with a points victory over Zach Parker in the Manchester arena.
The Olympic bronze medallist's activity level likely gained him a split decision in a competitive 10-round contest at the boxing arena.
But Parker found success, connecting with powerful single shots in a contest where the styles never quite clicked, with excessive holding marring the fight.
The scoring judges scored it 96-94 for to Buatsi, with the remaining official a even score.
"It wasn't my best display but how do champions respond? They succeed," Buatsi commented in the ring as he was met by negative reactions from the crowd.
The Londoner returned to winning ways after his initial pro loss - an thrilling contest with his previous opponent in February - to claim a twentieth professional win.
Several boxing experts thought the challenger, 31, should have been awarded the win but the British boxer experienced the second setback of his 28-match professional journey.
Buatsi Earns Triumph in Slow Affair
His career development has slowed in recent times through contract problems and extended periods of inactivity.
Earlier forecast as the next star of UK boxing, he now is positioned trying to realize his potential - possibly in what feels like a last chance - under new promotional backing.
He began cautiously, with both competitors ready to take risks in a calculated initial rounds.
The challenger, whose sole prior loss came at super middleweight against John Ryder in two years ago after suffering a hand injury during the bout, was participating in his second bout at light heavyweight.
By the fight's midpoint, Parker had stayed in contention, causing problems for the favorite, who worked behind a tight guard to barely take the cleaner periods.
The crowd's patience decreased amid frequent holding, with Parker slipping to the canvas several times during close exchanges.
Parker ended stronger, but multiple periods were difficult to score. However, previous titleholder the boxing analyst - working with the broadcast network - had it strongly leaning for the challenger, giving Buatsi just one round.
The victor progresses, but with the presence of hard hitter David Benavidez, and Russian star Dmitry Bivol dominating the weight class, the road to world glory - judging by this showing - still appears challenging.
Hatton Tribute Inspires All-Manchester Battle
In the supporting bout, Lyndon Arthur beat Bradley Rea by split-decision in a outstanding all-Manchester contest to capture the continental title.
The stadium grew hushed for a profoundly moving tribute before the fight as 10 bells sounded in honor of local hero Ricky Hatton, who died 46 years old in recently.
It was the first major televised match card in the location since Hatton's death. As the last bell ended, the silence gave way to a shout of "there's only one Hatton".
The fighting during the bout reflected the feeling. Arthur was knocked down by a powerful punch directly to the chin in the initial stage, getting up unsteadily to his footing on the referee's count.
But the red-colored equipment of the fighter soon pressed ahead again. On the opposite side, Rea - in rival City blue - was damaged soon, significant bruising developing under his orbital area as the duo landed punishing blows.
The challenger, 27, connected with strong blows but the champion, thirty-four, responded in kind with effective uppercuts as the intensity seldom decreased over 12 rounds.
Arthur edged the verdict with judges scorecards of even score, narrow lead and clearer margin, but both fighters were persistent and full of heart, everything their idol the legend represented.
