UK light-heavyweight Buatsi earned a win yet unimpressive debut to his career under fresh promotional backing with a points victory over Zach Parker in the Manchester arena.
The Olympic bronze medallist's punch output likely gained him a majority decision in a competitive ten-round fight at the Co-op Live Arena.
But Parker landed significant shots, delivering effective clean blows in a match where the approaches didn't complement each other, with frequent clinching spoiling the action.
Two judges had it 96-94 for to Buatsi, with the third a 95-95 draw.
"It wasn't my greatest showing but how do champions respond? They prevail," the victor commented in the ringside as he was greeted with boos from the crowd.
The Londoner bounced back after his first professional defeat - an thrilling contest with Callum Smith in last winter - to claim a twentieth professional win.
Various analysts felt Parker, thirty-one, merited the win but the contender experienced the second defeat of his 28-match professional journey.
The Champion Earns Victory in Uneventful Encounter
Buatsi's progress has plateaued in the past few years through promotional disputes and long spells of inactivity.
Once tipped as the next star of British boxing, he now stands trying to fulfil that early promise - perhaps in what seems like a final roll of the dice - under recent support.
He started carefully, with both competitors prepared to be aggressive in a tentative opening few rounds.
The challenger, whose sole prior loss came at super-middleweight against his former opponent in 2022 after suffering a hand injury during the bout, was competing in only his second appearance at light heavyweight.
By the middle rounds, Parker had stayed in contention, making life awkward for the favorite, who utilized a solid defense to barely take the better stanzas.
The spectators' acceptance wore thin amid frequent holding, with Parker going down various instances during close exchanges.
The underdog closed well, but several stanzas were hard to judge. Nevertheless, ex-champion the boxing analyst - commentating on the broadcast network - had it significantly in favor for Parker, giving Buatsi just one round.
Buatsi advances, but with the caliber of hard hitter David Benavidez, and Eastern European fighter Bivol leading the category, the road to world glory - on this evidence - still looks steep.
Hatton Memorial Motivates All-Manchester Fight
In the co-main event, Lyndon Arthur overcame Bradley Rea by divided decision in a outstanding Manchester vs Manchester contest to win the European light heavyweight belt.
The venue fell silent for a extremely emotional homage ahead of the contest as ten bells rang in memory of Manchester's own Ricky Hatton, who passed away 46 years old in recently.
It was the initial significant broadcast match card in the city since Hatton's passing. As the last bell faded, the quiet transitioned to a shout of "there's just one Ricky Hatton".
The competition within the ring matched the feeling. The eventual winner was sent to the canvas by a left hook squarely on the jaw in the second round, rising shakily to his feet on the eight count.
But the red-colored attire of Arthur soon came forward again. From the other corner, Rea - in opposing blue - was injured early, significant bruising developing under his orbital area as the duo landed powerful shots.
Rea, 27, connected with strong blows but the champion, thirty-four, matched the intensity with effective uppercuts as the pace rarely dropped over the full distance.
Arthur barely secured the verdict with official scores of 114-114, 115-113 and clearer margin, but both fighters were determined and courageous, all the qualities their hero Hatton represented.
