British light-heavyweight Buatsi secured a victory yet unimpressive debut to life under new promoters with a decision win over Zach Parker in Manchester.
The Olympic medal winner's work rate likely gained him a judges' verdict in a competitive 10-round bout at the Co-op Live Arena.
But Parker had his moments, delivering effective single shots in a fight where the styles failed to mesh, with excessive holding disrupting the fight.
Two judges had it 96-94 to the winner, with the remaining official a 95-95 draw.
"It wasn't my finest showing but what do champions do? They win," the victor said in the ringside as he was greeted with boos from the spectators.
The Londoner returned to winning ways after his maiden career setback - an memorable fight with his previous opponent in last winter - to earn a twentieth professional win.
Some ringside observers thought Parker, 31, should have been awarded the win but the Derbyshire fighter suffered the second defeat of his 28-bout career.
Buatsi Claims Triumph in Dull Match
The fighter's advancement has plateaued in the past few years through management issues and long spells of inactivity.
Earlier forecast as the future of UK boxing, he now is positioned trying to fulfil that early promise - perhaps in what seems like a final roll of the dice - under new promotional backing.
He started carefully, with neither fighter ready to overcommit in a calculated opening few rounds.
Parker, whose single earlier setback came at the lower weight class against his former opponent in 2022 after suffering a hand injury in the contest, was participating in his second bout at light heavyweight.
By the halfway stage, the underdog had made it competitive, causing problems for Buatsi, who operated with a solid defense to barely take the better periods.
The audience's tolerance wore thin during regular grabbing, with Parker going down multiple occasions during grappling.
Parker closed well, but several stanzas were challenging to assess. However, former world champion Carl Frampton - providing analysis for Dazn - had it strongly leaning for the challenger, scoring for Buatsi just only one stanza.
Buatsi progresses, but with the likes of power puncher Benavidez, and Russian star Dmitry Bivol dominating the weight class, the path to championship success - judging by this showing - still appears challenging.
Hatton Homage Inspires Manchester Derby Battle
In the co-main event, Lyndon Arthur defeated Bradley Rea by split-decision in a excellent local rivalry fight to win the European light-heavyweight title.
The arena fell silent for a profoundly moving homage ahead of the contest as ten bells rang in honor of local hero Ricky Hatton, who succumbed 46 years old in recently.
It was the initial significant broadcast fight night in the city since Hatton's death. As the concluding sound disappeared, the silence transitioned to a shout of "only one Ricky Hatton".
The action inside the ropes equaled the emotion. The eventual winner was sent to the canvas by a left hook squarely on the face in the initial stage, getting up unsteadily to his footing on the eight count.
But the Manchester United-red attire of the fighter soon advanced again. From the other corner, the opponent - in opposing blue - was damaged soon, noticeable damage appearing under his orbital area as the duo traded punishing blows.
The challenger, twenty-seven, delivered effective strikes but the champion, thirty-four, responded in kind with stinging uppercuts as the intensity rarely dropped over the full distance.
Arthur edged the verdict with scoring tallies of 114-114, narrow lead and clearer margin, but both fighters were relentless and brave, all the qualities their idol the legend represented.
