British light heavyweight Buatsi earned a win yet underwhelming beginning to life under fresh promotional backing with a decision win over Zach Parker in the Manchester arena.
The Olympic bronze medallist's punch output likely gained him a majority decision in a tight ten-round fight at the Manchester venue.
But Parker landed significant shots, connecting with powerful clean blows in a contest where the approaches never quite clicked, with constant grabbing marring the action.
Two judges judged it 96-94 to Buatsi, with the remaining official a even score.
"It wasn't my finest performance but what defines champions? They prevail," Buatsi commented in the ring as he was greeted with disapproval from the crowd.
The Londoner returned to winning ways after his maiden career setback - an memorable fight with Callum Smith in last winter - to secure a twentieth professional win.
Several boxing experts felt Parker, thirty-one, deserved the win but the British boxer experienced the second defeat of his 28-fight professional journey.
The Champion Claims Win in Uneventful Encounter
Buatsi's progress has slowed in recent times through management issues and long spells of inactivity.
Earlier forecast as the future of British boxing, he now stands trying to achieve expectations - maybe in what appears to be a ultimate opportunity - under new promotional backing.
He started carefully, with neither fighter willing to take risks in a tentative opening few rounds.
Parker, whose single earlier setback came at super-middleweight against John Ryder in two years ago after damaging his hand 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 the favorite, who worked behind a tight guard to barely take the better periods.
The spectators' acceptance decreased because of frequent holding, with the challenger going down several times during clinches.
Parker finished the stronger, but multiple periods were challenging to assess. However, ex-champion Carl Frampton - providing analysis for Dazn - had it significantly in favor for the challenger, giving Buatsi just only one stanza.
Buatsi advances, but with the caliber of power puncher Benavidez, and Eastern European fighter Dmitry Bivol leading the category, the path to championship success - on this evidence - still appears challenging.
Ricky Hatton Homage Motivates Manchester Derby Fight
In the co-main event, Lyndon Arthur overcame Rea by divided decision in a terrific local rivalry fight to win the European light-heavyweight championship.
The stadium fell silent for a profoundly moving memorial ahead of the contest as 10 bells rang in memory of Manchester's own Hatton, who passed away aged 46 in recently.
It was the premier televised match card in the location since Hatton's passing. As the final chime ended, the silence gave way to a roar of "there's only one Hatton".
The fighting inside the ropes equaled the emotion. The eventual winner was knocked down by a significant blow directly to the face in the early round, getting up unsteadily to his feet on the eight count.
But the red-colored equipment of the fighter soon pressed ahead again. From the other corner, Rea - in rival City blue - was damaged soon, heavy swelling appearing under his eye as the fighters landed hard punches.
The challenger, 27, delivered effective strikes but Arthur, 34, fought fire with fire with effective uppercuts as the intensity rarely dropped over the full distance.
Arthur edged the result with scoring tallies of even score, narrow lead and 115-112, but the two athletes were relentless and full of heart, everything their idol the legend stood for.
