British light heavyweight Buatsi earned a win yet disappointing beginning to his career under new promoters with a unanimous decision over Zach Parker in the Manchester arena.
The Olympic medal winner's punch output likely gained him a majority decision in a competitive 10-round bout at the boxing arena.
But Parker had his moments, connecting with powerful individual punches in a contest where the techniques didn't complement each other, with constant grabbing marring the action.
The scoring judges scored it 96-94 in favor to the winner, with the remaining official a even score.
"It wasn't my greatest showing but what do champions do? They prevail," Buatsi said in the ring as he was faced boos from the crowd.
The Londoner returned to winning ways after his first professional defeat - an memorable fight with his previous opponent in February - to secure a 20th pro success.
Several boxing experts believed Parker, thirty-one, merited the win but the British boxer suffered the second defeat of his 28-fight career.
Buatsi Secures Triumph in Slow Match
His career development has plateaued in recent years through promotional disputes and long spells of lack of fights.
Earlier forecast as the next star of the British fight scene, he now is positioned trying to realize his potential - perhaps in what seems like a last chance - under new promotional backing.
He began cautiously, with both competitors prepared to overcommit in a tentative opening few rounds.
The challenger, whose sole prior loss came at super middleweight against John Ryder in 2022 after damaging his hand mid-fight, was competing in only his second bout at light heavyweight.
By the fight's midpoint, the underdog had kept it close, making life awkward for Buatsi, who operated with a tight guard to edge the better periods.
The spectators' acceptance diminished because of frequent holding, with the challenger falling to the floor various instances during clinches.
The underdog ended stronger, but multiple periods were hard to judge. Nevertheless, ex-champion the boxing analyst - working with the broadcast network - had it strongly leaning for Parker, awarding Buatsi just only one stanza.
The victor progresses, but with the likes of heavy hitter David Benavidez, and Eastern European fighter Dmitry Bivol ruling the division, the journey to titles - judging by this showing - still looks steep.
Hatton Tribute Fuels Manchester Derby Fight
In the secondary fight, Lyndon Arthur overcame Rea by split-decision in a outstanding Manchester vs Manchester battle to secure the continental title.
The arena became quiet for a deeply poignant tribute before the fight as a bell ceremony sounded in memory of Manchester's own Ricky Hatton, who died 46 years old in recently.
It was the premier televised boxing event in the location since the passing of Hatton. As the final chime disappeared, the silence became a roar of "only one Ricky Hatton".
The fighting inside the ropes matched the sentiment. Arthur was floored by a left hook flush on the chin in the second round, standing uncertainly to his feet on the count of eight.
But the Manchester United-red shorts of Arthur soon pressed ahead again. On the opposite side, the opponent - in rival City blue - was injured quickly, noticeable damage appearing under his orbital area as the pair landed hard punches.
The challenger, 27, connected with strong blows but the champion, thirty-four, responded in kind with stinging uppercuts as the action rarely dropped over 12 rounds.
The victor edged the decision with official scores of even score, narrow lead and wider gap, but each competitor were determined and courageous, exactly what their idol the legend represented.
