British light heavyweight Buatsi made a winning yet underwhelming debut to life under new promoters with a points victory over Zach Parker in Manchester.
The Olympic bronze medallist's punch output appeared to earn him a majority decision in a tight ten-round fight at the Manchester venue.
But Parker landed significant shots, delivering effective clean blows in a match where the techniques never quite clicked, with constant grabbing marring the action.
Two judges had it 96-94 to Buatsi, with the final judge a 95-95.
"It wasn't my finest showing but what defines champions? They prevail," Buatsi said in the ringside as he was faced negative reactions from the crowd.
The Londoner bounced back after his initial pro loss - an epic battle with his previous opponent in last winter - to claim a 20th pro success.
Some ringside observers thought the challenger, thirty-one, deserved the decision but the British boxer endured the second loss of his 28-bout professional journey.
Buatsi Secures Triumph in Slow Match
His career development has stalled in the past few years through promotional disputes and considerable time of inactivity.
Previously predicted as the next star of British boxing, he now finds himself trying to fulfil that early promise - maybe in what feels like a final roll of the dice - under recent support.
He began cautiously, with both competitors prepared to take risks in a cagey opening few rounds.
Parker, whose only previous defeat came at super middleweight against his former opponent in 2022 after suffering a hand injury during the bout, was participating in his second appearance at the higher weight class.
By the middle rounds, the underdog had kept it close, making life awkward for the favorite, who utilized a solid defense to barely take the more effective rounds.
The spectators' acceptance wore thin amid regular grabbing, with Parker going down various instances during grappling.
Parker ended stronger, but many rounds were difficult to score. Nevertheless, former world champion the boxing analyst - providing analysis for the broadcast network - had it significantly in favor for Parker, awarding Buatsi just a single round.
The victor moves on, but with the caliber of hard hitter David Benavidez, and Russian champion Dmitry Bivol ruling the division, the path to championship success - judging by this showing - still appears challenging.
Ricky Hatton Tribute Inspires Local Rivalry Battle
In the supporting bout, Lyndon Arthur beat Bradley Rea by split-decision in a outstanding all-Manchester fight to secure the continental title.
The venue grew hushed for a deeply poignant homage ahead of the contest as ten bells tolled in honor of Manchester's own Ricky Hatton, who died aged 46 in recently.
It was the initial significant broadcast match card in the city since Hatton's death. As the final chime faded, the silence gave way to a chant of "there's just one Ricky Hatton".
The competition during the bout equaled the emotion. Arthur was floored by a powerful punch squarely on the chin in the initial stage, standing uncertainly to his footing on the eight count.
But the traditional red equipment of Arthur soon advanced again. Across the ring, the opponent - in competitive blue - was damaged soon, significant bruising developing under his orbital area as the duo landed hard punches.
Rea, 27, delivered effective strikes but the champion, thirty-four, matched the intensity with stinging uppercuts as the action rarely dropped over twelve rounds.
Arthur narrowly won the verdict with official scores of 114-114, 115-113 and clearer margin, but each competitor were persistent and full of heart, all the qualities their hero Hatton embodied.
