UK light heavyweight Buatsi earned a win yet disappointing start to life under new promoters with a points victory over Zach Parker in Manchester.
The Olympic medal winner's punch output seemingly secured him a split decision in a competitive 10-round bout at the Manchester venue.
But Parker found success, landing some telling clean blows in a fight where the styles failed to mesh, with frequent clinching disrupting the action.
The officials had it 96-94 for to the winner, with the third a 95-95 draw.
"It wasn't my greatest display but how do champions respond? They succeed," the victor stated in the arena as he was faced disapproval from the audience.
The Londoner got back to winning after his first professional defeat - an memorable fight with Callum Smith in last winter - to claim a 20th pro success.
Some ringside observers thought Parker, thirty-one, should have been awarded the decision but the British boxer experienced the second defeat of his 28-fight career.
Buatsi Claims Win in Dull Encounter
His career development has slowed in recent times through management issues and long spells of lack of fights.
Earlier forecast as the rising talent of British boxing, he now stands trying to realize his potential - possibly in what seems like a final roll of the dice - under recent support.
He opened tentatively, with both competitors willing to overcommit in a cagey early stages.
Parker, whose only previous defeat came at super middleweight against John Ryder in two years ago after damaging his hand mid-fight, was making just his second appearance at light-heavyweight.
By the fight's midpoint, the underdog had stayed in contention, creating difficulties for Buatsi, who operated with a tight guard to narrowly win the more effective stanzas.
The spectators' acceptance diminished because of constant clinching, with the challenger falling to the floor various instances during grappling.
The underdog closed well, but several stanzas were challenging to assess. However, previous titleholder the boxing analyst - commentating on the broadcast network - had it particularly wide for the challenger, awarding Buatsi just only one stanza.
The victor progresses, but with the presence of power puncher Benavidez, and Russian star Dmitry Bivol dominating the weight class, the path to championship success - judging by this showing - still seems difficult.
Hatton Memorial Inspires Local Rivalry Fight
In the co-main event, Lyndon Arthur overcame Rea by divided decision in a excellent Manchester vs Manchester contest to secure the European light-heavyweight belt.
The venue grew hushed for a extremely emotional tribute prior to the bout as a bell ceremony tolled in remembrance of Manchester's own Ricky Hatton, who succumbed 46 years old in last month.
It was the premier televised boxing event in the urban center since the passing of Hatton. As the concluding sound disappeared, the quiet gave way to a shout of "there's only one Hatton".
The action during the bout reflected the emotion. The eventual winner was sent to the canvas by a significant blow flush on the jaw in the early round, standing uncertainly to his position on the referee's count.
But the red-colored attire of Arthur soon pressed ahead again. From the other corner, Rea - in rival City blue - was marked up early, noticeable damage developing under his face as the duo exchanged punishing blows.
The challenger, 27, connected with strong blows but Arthur, thirty-four, responded in kind with effective uppercuts as the pace rarely dropped over twelve rounds.
The victor edged the verdict with official scores of 114-114, 115-113 and clearer margin, but the two athletes were persistent and brave, exactly what their inspiration the legend stood for.
