British light heavyweight Buatsi secured a victory yet unimpressive start to his career under recent management with a points victory over Zach Parker in the Manchester arena.
The Olympic medal winner's activity level appeared to earn him a majority decision in a close ten-round contest at the Co-op Live Arena.
But the challenger landed significant shots, delivering effective single shots in a contest where the techniques failed to mesh, with constant grabbing disrupting the contest.
The officials had it 96-94 to the winner, with the remaining official a even score.
"It wasn't my finest showing but what do champions do? They win," Buatsi commented in the arena as he was faced negative reactions from the audience.
The Londoner bounced back after his initial pro loss - an epic battle with Callum Smith in February - to earn a 20th pro success.
Various analysts thought the challenger, 31, deserved the win but the British boxer endured the second defeat of his 28-match professional journey.
The Champion Claims Win in Uneventful Affair
Buatsi's progress has plateaued in recent years through promotional disputes and long spells of inactivity.
Previously predicted as the future of UK boxing, he now is positioned trying to achieve expectations - perhaps in what feels like a last chance - under fresh management.
He opened tentatively, with the two boxers willing to be aggressive in a tentative early stages.
The challenger, whose single earlier setback came at the lower weight class against his former opponent in 2022 after suffering a hand injury during the bout, was competing in only his second fight at light-heavyweight.
By the middle rounds, Parker had made it competitive, creating difficulties for Buatsi, who operated with a protective stance to edge the better periods.
The audience's tolerance decreased during frequent holding, with Parker slipping to the canvas several times during close exchanges.
The underdog ended stronger, but several stanzas were difficult to score. Although, ex-champion the boxing analyst - providing analysis for Dazn - had it particularly wide for the challenger, giving Buatsi just one round.
Buatsi moves on, but with the likes of power puncher Benavidez, and Russian champion Bivol dominating the weight class, the journey to titles - based on this performance - still looks steep.
Ricky Hatton Tribute Motivates All-Manchester Battle
In the secondary fight, Lyndon Arthur overcame Rea by split-decision in a outstanding Manchester vs Manchester contest to win the European light-heavyweight title.
The stadium grew hushed for a profoundly moving homage ahead of the contest as ten bells sounded in memory of Manchester's own Hatton, who died 46 years old in last month.
It was the first major televised match card in the location since the passing of Hatton. As the last bell ended, the quiet transitioned to a roar of "only one Ricky Hatton".
The action within the ring equaled the emotion. The eventual winner was knocked down by a powerful punch flush on the chin in the initial stage, rising shakily to his feet on the count of eight.
But the red-colored shorts of Arthur soon came forward again. On the opposite side, the opponent - in rival City blue - was marked up early, noticeable damage forming under his face as the fighters exchanged punishing blows.
Rea, twenty-seven, delivered effective strikes but the champion, 34, fought fire with fire with effective uppercuts as the pace rarely dropped over the full distance.
Arthur narrowly won the result with scoring tallies of even score, 115-113 and 115-112, but each competitor were relentless and courageous, exactly what their hero the legend embodied.
