UK light heavyweight Buatsi earned a win yet disappointing debut to life under recent management with a points victory over Zach Parker in Manchester.
The Olympic bronze medallist's work rate likely gained him a judges' verdict in a tight ten-round fight at the Co-op Live Arena.
But the challenger landed significant shots, connecting with powerful individual punches in a match where the techniques failed to mesh, with excessive holding spoiling the action.
The scoring judges had it 96-94 for to the winner, with the final judge a 95-95.
"It wasn't my best display but how do champions respond? They win," the victor stated in the arena as he was faced disapproval from the spectators.
The Londoner bounced back after his first professional defeat - an epic battle with his previous opponent in February - to claim a 20th career victory.
Several boxing experts felt the challenger, thirty-one, deserved the win but the Derbyshire fighter experienced the second defeat of his 28-match career.
Buatsi Claims Win in Uneventful Affair
Buatsi's progress has slowed in recent years through contract problems and long spells of lack of fights.
Earlier forecast as the next star of British boxing, he now finds himself trying to fulfil that early promise - possibly in what seems like a last chance - under recent support.
He started carefully, with both competitors prepared to take risks in a tentative opening few rounds.
The challenger, whose sole prior loss came at super-middleweight against John Ryder in 2022 after damaging his hand during the bout, was making just his second fight at the higher weight class.
By the fight's midpoint, the underdog had kept it close, causing problems for Buatsi, who utilized a tight guard to narrowly win the cleaner rounds.
The spectators' acceptance diminished during frequent holding, with Parker slipping to the canvas multiple occasions during grappling.
The underdog closed well, but many rounds were hard to judge. Although, former world champion Carl Frampton - commentating on Dazn - had it significantly in favor for the challenger, scoring for Buatsi just only one stanza.
Buatsi advances, but with the presence of power puncher Benavidez, and Eastern European fighter Dmitry Bivol leading the category, the road to world glory - on this evidence - still appears challenging.
Ricky Hatton Memorial Motivates Local Rivalry Contest
In the co-main event, Lyndon Arthur defeated Bradley Rea by divided decision in a terrific Manchester vs Manchester battle to secure the European light heavyweight championship.
The venue grew hushed for a extremely emotional memorial prior to the bout as a bell ceremony sounded in memory of local hero Ricky Hatton, who died at age 46 in September.
It was the first major televised fight night in the location since the passing of Hatton. As the last bell ended, the silence transitioned to a roar of "there's only one Hatton".
The competition inside the ropes equaled the sentiment. Arthur was floored by a left hook directly to the jaw in the initial stage, getting up unsteadily to his position on the eight count.
But the traditional red attire of the fighter soon advanced again. Across the ring, Rea - in competitive blue - was marked up soon, heavy swelling appearing under his orbital area as the fighters landed powerful shots.
Rea, 27, landed power punches but Arthur, 34, responded in kind with powerful upward punches as the pace rarely dropped over the full distance.
The victor narrowly won the verdict with judges scorecards of even score, 115-113 and wider gap, but both fighters were persistent and courageous, everything their inspiration the legend embodied.
