UK light heavyweight Buatsi earned a win yet underwhelming debut to life under new promoters with a unanimous decision over Zach Parker in Manchester.
The Olympic medal winner's punch output seemingly secured him a majority decision in a close ten-round fight at the Co-op Live Arena.
But the challenger found success, landing some telling individual punches in a contest where the techniques never quite clicked, with constant grabbing spoiling the fight.
The scoring judges judged it 96-94 for to Buatsi, with the remaining official a 95-95 draw.
"It wasn't my best performance but how do champions respond? They win," Buatsi said in the ring as he was met by disapproval from the audience.
The British fighter bounced back after his initial pro loss - an epic battle with Callum Smith in last winter - to secure a 20th pro success.
Some ringside observers thought the challenger, 31, merited the victory but the British boxer endured the second setback of his 28-match professional journey.
The Champion Claims Victory in Uneventful Affair
His career development has plateaued in recent years through contract problems and considerable time of inactivity.
Earlier forecast as the rising talent of the British fight scene, 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 the two boxers ready to overcommit in a cagey early stages.
The challenger, whose sole prior loss came at super middleweight against his former opponent in 2022 after damaging his hand during the bout, was competing in only his second fight at light heavyweight.
By the fight's midpoint, Parker had kept it close, causing problems for the favorite, who utilized a tight guard to edge the cleaner periods.
The crowd's patience wore thin because of frequent holding, with the challenger going down various instances during close exchanges.
Parker finished the stronger, but many rounds were difficult to score. Nevertheless, previous titleholder Carl Frampton - working with the broadcast network - had it significantly in favor for the challenger, awarding Buatsi just one round.
Buatsi moves on, but with the caliber of power puncher David Benavidez, and Russian star Bivol leading the category, the road to world glory - judging by this showing - still appears challenging.
Hatton Memorial Fuels All-Manchester Battle
In the secondary fight, Lyndon Arthur overcame Rea by split-decision in a excellent Manchester vs Manchester fight to win the European light heavyweight title.
The venue became quiet for a extremely emotional homage before the fight as a bell ceremony sounded in memory of Manchester's own Hatton, who succumbed 46 years old 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 roar of "there's just one Hatton".
The fighting inside the ropes reflected the feeling. Arthur was knocked down by a significant blow squarely on the chin in the second round, getting up unsteadily to his position on the eight count.
But the Manchester United-red shorts of the fighter soon pressed ahead again. On the opposite side, the opponent - in rival City blue - was injured quickly, significant bruising developing under his orbital area as the duo traded powerful shots.
The challenger, 27, landed power punches but the champion, thirty-four, matched the intensity with stinging uppercuts as the pace hardly diminished over twelve rounds.
Arthur barely secured the result with official scores of draw, 115-113 and wider gap, but each competitor were determined and full of heart, everything their hero the legend stood for.
