UK light-heavyweight Buatsi made a winning yet unimpressive debut to life under recent management with a decision win over Zach Parker in the Manchester arena.
The Olympic medal winner's punch output appeared to earn him a split decision in a competitive ten-round bout at the Manchester venue.
But the challenger landed significant shots, connecting with powerful individual punches in a fight where the approaches failed to mesh, with frequent clinching spoiling the contest.
The scoring judges scored it 96-94 to the winner, with the final judge a 95-95 draw.
"It wasn't my finest performance but how do champions respond? They prevail," the victor said in the ring as he was greeted with disapproval from the crowd.
The Londoner returned to winning ways after his initial pro loss - an memorable fight with Callum Smith in last winter - to claim a 20th pro success.
Various analysts believed the challenger, thirty-one, should have been awarded the win but the British boxer endured the second loss of his 28-match professional journey.
Buatsi Earns Win in Slow Encounter
The fighter's advancement has slowed in the past few years through contract problems and considerable time of inactivity.
Earlier forecast as the next star of British boxing, he now is positioned trying to fulfil that early promise - perhaps in what seems like a ultimate opportunity - under new promotional backing.
He started carefully, with the two boxers willing to be aggressive in a tentative early stages.
The challenger, whose sole prior loss came at super-middleweight against his former opponent in two years ago after breaking his hand during the bout, was competing in only his second appearance at the higher weight class.
By the halfway stage, the underdog had stayed in contention, creating difficulties for the favorite, who worked behind a protective stance to barely take the more effective stanzas.
The crowd's patience decreased during frequent holding, with Parker slipping to the canvas several times during close exchanges.
The underdog ended stronger, but multiple periods were challenging to assess. However, previous titleholder the boxing analyst - commentating on Dazn - had it particularly wide for Parker, awarding Buatsi just a single round.
Buatsi progresses, but with the presence of power puncher Benavidez, and Russian star Dmitry Bivol leading the category, the road to world glory - on this evidence - still appears challenging.
Hatton Memorial Inspires Local Rivalry Fight
In the co-main event, Lyndon Arthur overcame Bradley Rea by split-decision in a outstanding Manchester vs Manchester contest to secure the European light heavyweight title.
The venue grew hushed for a profoundly moving memorial before the fight as ten bells tolled in remembrance of Manchester's own Ricky Hatton, who passed away aged 46 in recently.
It was the premier televised fight night in the city since Hatton's death. As the final chime disappeared, the silence gave way to a chant of "there's just one Hatton".
The competition inside the ropes reflected the feeling. Arthur was sent to the canvas by a left hook directly to the face in the initial stage, standing uncertainly to his feet on the referee's count.
But the Manchester United-red equipment of Arthur soon advanced again. Across the ring, the opponent - in competitive blue - was marked up soon, noticeable damage forming under his eye as the fighters exchanged hard punches.
Rea, 27, delivered effective strikes but the champion, thirty-four, matched the intensity with powerful upward punches as the action hardly diminished over the full distance.
Arthur narrowly won the decision with official scores of draw, close margin and clearer margin, but each competitor were relentless and full of heart, all the qualities their hero Hatton represented.
