British light-heavyweight Buatsi made a winning yet disappointing start to his career under fresh promotional backing with a unanimous decision over Zach Parker in the Manchester arena.
The Olympic bronze medallist's work rate appeared to earn him a majority decision in a close ten-round fight at the Co-op Live Arena.
But Parker landed significant shots, delivering effective clean blows in a contest where the techniques never quite clicked, with constant grabbing marring the contest.
Two judges scored it 96-94 in favor to Buatsi, with the third a even score.
"It wasn't my finest performance but what do champions do? They prevail," the victor stated in the ringside as he was met by boos from the crowd.
The British fighter returned to winning ways after his maiden career setback - an epic battle with his previous opponent in February - to claim a 20th pro success.
Some ringside observers believed Parker, 31, should have been awarded the win but the British boxer suffered the second setback of his 28-bout professional journey.
Buatsi Earns Triumph in Dull Match
The fighter's advancement has stalled in the past few years through management issues and long spells of lack of fights.
Previously predicted as the future of UK boxing, he now is positioned trying to realize his potential - perhaps in what feels like a last chance - under fresh management.
He started carefully, with neither fighter willing to be aggressive in a cagey early stages.
Parker, whose single earlier setback came at super middleweight against John Ryder in 2022 after damaging his hand mid-fight, was making just his second bout at the higher weight class.
By the halfway stage, the underdog had kept it close, creating difficulties for the favorite, who operated with a protective stance to narrowly win the cleaner stanzas.
The audience's tolerance decreased because of regular grabbing, with the challenger slipping to the canvas multiple occasions during clinches.
The underdog ended stronger, but several stanzas were challenging to assess. Nevertheless, former world champion Carl Frampton - commentating on Dazn - had it significantly in favor for Parker, awarding Buatsi just only one stanza.
Buatsi advances, but with the presence of heavy hitter Benavidez, and Russian star Dmitry Bivol dominating the weight class, the journey to titles - based on this performance - still seems difficult.
Ricky Hatton Homage Fuels Manchester Derby Fight
In the supporting bout, Lyndon Arthur overcame Bradley Rea by close verdict in a excellent all-Manchester battle to capture the continental championship.
The stadium fell silent for a extremely emotional tribute prior to the bout as a bell ceremony tolled in honor of Manchester's own Hatton, who passed away 46 years old in last month.
It was the premier televised fight night in the urban center since Hatton's death. As the final chime faded, the quiet transitioned to a shout of "there's only one Ricky Hatton".
The fighting within the ring equaled the sentiment. Arthur was floored by a significant blow directly to the chin in the early round, standing uncertainly to his position on the count of eight.
But the Manchester United-red attire of the fighter soon advanced again. On the opposite side, Rea - in opposing blue - was damaged soon, noticeable damage appearing under his eye as the fighters exchanged powerful shots.
The challenger, 27, connected with strong blows but the champion, 34, fought fire with fire with powerful upward punches as the pace hardly diminished over the full distance.
Arthur barely secured the result with scoring tallies of even score, 115-113 and wider gap, but each competitor were relentless and brave, all the qualities their inspiration Hatton represented.
