UK light heavyweight Buatsi earned a win yet unimpressive beginning to his career under fresh promotional backing with a decision win over Zach Parker in the Manchester arena.
The Olympic medal winner's work rate likely gained him a split decision in a close ten-round fight at the Co-op Live Arena.
But Parker found success, delivering effective single shots in a match where the techniques never quite clicked, with constant grabbing spoiling the contest.
Two judges judged it 96-94 for to the winner, with the third a even score.
"It wasn't my best performance but how do champions respond? They win," Buatsi said in the arena as he was met by boos from the crowd.
The British fighter returned to winning ways after his initial pro loss - an epic battle with Callum Smith in last winter - to secure a twentieth professional win.
Various analysts felt Parker, thirty-one, merited the victory but the contender suffered the second setback of his 28-match professional journey.
The Champion Secures Triumph in Uneventful Encounter
Buatsi's progress has stalled in recent years through management issues and long spells of inactivity.
Previously predicted as the future of British boxing, he now finds himself trying to fulfil that early promise - perhaps in what feels like a ultimate opportunity - under fresh management.
He opened tentatively, with neither fighter prepared to overcommit in a calculated opening few rounds.
The challenger, whose single earlier setback came at super middleweight against his former opponent in two years ago after breaking his hand mid-fight, was making just his second fight at light heavyweight.
By the halfway stage, the underdog had made it competitive, creating difficulties for Buatsi, who operated with a tight guard to barely take the better rounds.
The crowd's patience wore thin during frequent holding, with the challenger going down various instances during clinches.
Parker closed well, but several stanzas were hard to judge. However, former world champion the boxing analyst - providing analysis for Dazn - had it particularly wide for the challenger, giving Buatsi just only one stanza.
The victor advances, but with the likes of hard hitter Benavidez, and Russian champion Dmitry Bivol leading the category, the path to championship success - based on this performance - still appears challenging.
Hatton Memorial Motivates All-Manchester Contest
In the co-main event, Arthur beat Rea by divided decision in a terrific all-Manchester contest to secure the European light-heavyweight belt.
The arena became quiet for a extremely emotional homage before the fight as ten bells sounded in honor of the city's native Ricky Hatton, who passed away aged 46 in September.
It was the first major televised match card in the city since Hatton's passing. As the final chime faded, the quiet became a roar of "there's just one Hatton".
The fighting inside the ropes reflected the emotion. Arthur was floored by a significant blow flush on the jaw in the second round, rising shakily to his footing on the count of eight.
But the red-colored equipment of Arthur soon came forward again. From the other corner, Rea - in competitive blue - was marked up quickly, significant bruising forming under his orbital area as the pair traded punishing blows.
Rea, twenty-seven, landed power punches but Arthur, 34, fought fire with fire with stinging uppercuts as the action seldom decreased over the full distance.
Arthur edged the verdict with scoring tallies of 114-114, close margin and 115-112, but the two athletes were determined and full of heart, everything their idol the legend embodied.
