UK light heavyweight Buatsi earned a win yet unimpressive beginning to life under fresh promotional backing with a decision win over Zach Parker in the Manchester arena.
The Olympic medal winner's work rate seemingly secured him a split decision in a tight 10-round contest at the Manchester venue.
But the challenger landed significant shots, landing some telling single shots in a contest where the styles never quite clicked, with excessive holding marring the fight.
The scoring judges judged it 96-94 in favor to Buatsi, with the final judge a 95-95 draw.
"It wasn't my greatest display but how do champions respond? They win," Buatsi commented in the ringside as he was met by boos from the audience.
The Londoner bounced back after his initial pro loss - an epic battle with his previous opponent in last winter - to claim a 20th career victory.
Several boxing experts felt the challenger, 31, merited the decision but the contender suffered the second defeat of his 28-match career.
The Champion Earns Victory in Uneventful Match
His career development has slowed in recent times through promotional disputes and considerable time of lack of fights.
Previously predicted as the next star of UK boxing, he now is positioned trying to realize his potential - maybe in what appears to be a ultimate opportunity - under fresh management.
He began cautiously, with neither fighter ready 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 suffering a hand injury mid-fight, was competing in only his second appearance at light heavyweight.
By the fight's midpoint, the underdog had made it competitive, creating difficulties for the favorite, who operated with a tight guard to edge the cleaner rounds.
The audience's tolerance wore thin because of frequent holding, with Parker going down multiple occasions during close exchanges.
The underdog ended stronger, but several stanzas were hard to judge. Although, previous titleholder the boxing analyst - providing analysis for the broadcast network - had it significantly in favor for the challenger, giving Buatsi just one round.
The victor progresses, but with the presence of hard hitter Benavidez, and Russian champion Bivol dominating the weight class, the journey to titles - judging by this showing - still looks steep.
Ricky Hatton Homage Fuels Local Rivalry Fight
In the supporting bout, Lyndon Arthur overcame Rea by split-decision in a terrific local rivalry battle to capture the continental belt.
The arena fell silent for a extremely emotional memorial ahead of the contest as ten bells sounded in honor of Manchester's own Ricky Hatton, who died 46 years old in recently.
It was the first major televised match card in the location since the passing of Hatton. As the final chime disappeared, the quiet transitioned to a roar of "there's only one Hatton".
The action within the ring reflected the emotion. Arthur was sent to the canvas by a significant blow flush on the chin in the initial stage, getting up unsteadily to his footing on the count of eight.
But the Manchester United-red attire of the fighter soon came forward again. Across the ring, Rea - in rival City blue - was injured early, significant bruising developing under his orbital area as the fighters exchanged hard punches.
The challenger, 27, landed power punches but Arthur, thirty-four, matched the intensity with stinging uppercuts as the intensity seldom decreased over 12 rounds.
Arthur edged the verdict with scoring tallies of even score, close margin and clearer margin, but both fighters were persistent and brave, all the qualities their idol Hatton represented.
