UK light-heavyweight Buatsi made a winning yet unimpressive start to life under recent management with a points victory over Zach Parker in Manchester.
The Olympic bronze medallist's activity level likely gained him a split decision in a competitive 10-round fight at the Manchester venue.
But Parker landed significant shots, connecting with powerful clean blows in a fight where the techniques never quite clicked, with excessive holding marring the contest.
Two judges scored it 96-94 to Buatsi, with the third a 95-95.
"It wasn't my greatest display but how do champions respond? They win," the victor stated in the arena as he was met by boos from the spectators.
The Londoner returned to winning ways after his initial pro loss - an thrilling contest with Callum Smith in last winter - to claim a 20th career victory.
Various analysts felt the challenger, thirty-one, merited the win but the contender experienced the second defeat of his 28-fight career.
The Champion Earns Victory in Uneventful Affair
Buatsi's progress has plateaued in the past few years through contract problems and considerable time of lack of fights.
Once tipped as the rising talent of UK boxing, he now is positioned trying to achieve expectations - possibly in what appears to be a last chance - under new promotional backing.
He opened tentatively, with neither fighter willing to overcommit in a tentative early stages.
Parker, whose only previous defeat came at super-middleweight against John Ryder in 2022 after suffering a hand injury during the bout, was competing in only his second appearance at the higher weight class.
By the fight's midpoint, Parker had made it competitive, making life awkward for the favorite, who utilized a solid defense to narrowly win the more effective rounds.
The crowd's patience wore thin amid frequent holding, with the challenger slipping to the canvas multiple occasions during close exchanges.
The underdog closed well, but many rounds were difficult to score. Although, previous titleholder the boxing analyst - providing analysis for Dazn - had it significantly in favor for Parker, giving Buatsi just a single round.
The victor advances, but with the likes of heavy hitter Benavidez, and Eastern European fighter Bivol ruling the division, the path to championship success - on this evidence - still seems difficult.
Hatton Homage Motivates All-Manchester Fight
In the co-main event, Lyndon Arthur defeated Rea by close verdict in a outstanding Manchester vs Manchester fight to win the European light-heavyweight championship.
The arena fell silent for a deeply poignant memorial prior to the bout as ten bells sounded in honor of the city's native Hatton, who succumbed at age 46 in September.
It was the first major televised boxing event in the city since the passing of Hatton. As the concluding sound disappeared, the stillness became a chant of "only one Ricky Hatton".
The action inside the ropes reflected the feeling. The eventual winner was sent to the canvas by a powerful punch flush on the chin in the initial stage, rising shakily to his footing on the count of eight.
But the traditional red equipment of Arthur soon pressed ahead again. Across the ring, the opponent - in rival City blue - was injured early, noticeable damage developing under his face as the pair landed hard punches.
Rea, 27, delivered effective strikes but Arthur, 34, responded in kind with stinging uppercuts as the action seldom decreased over 12 rounds.
Arthur edged the verdict with official scores of even score, close margin and clearer margin, but each competitor were relentless and courageous, all the qualities their hero Hatton stood for.
