UK light heavyweight Buatsi secured a victory yet unimpressive debut to his career under new promoters with a points victory over Zach Parker in the Manchester arena.
The Olympic medal winner's punch output appeared to earn him a judges' verdict in a tight ten-round bout at the boxing arena.
But Parker landed significant shots, landing some telling single shots in a match where the styles failed to mesh, with constant grabbing disrupting the contest.
Two judges scored it 96-94 in favor to Buatsi, with the final judge a even score.
"It wasn't my best showing but what defines champions? They win," Buatsi stated in the ringside as he was met by disapproval from the audience.
The Londoner returned to winning ways after his maiden career setback - an epic battle with Callum Smith in last winter - to claim a twentieth professional win.
Several boxing experts felt the challenger, thirty-one, should have been awarded the decision but the Derbyshire fighter experienced the second defeat of his 28-match professional journey.
Buatsi Earns Victory in Dull Affair
Buatsi's progress has plateaued in the past few years through promotional disputes and extended periods of lack of fights.
Previously predicted as the future of the British fight scene, he now finds himself trying to realize his potential - maybe in what seems like a final roll of the dice - under recent support.
He started carefully, with neither fighter willing to take risks in a cagey initial rounds.
Parker, whose sole prior loss came at super-middleweight against John Ryder in two years ago after suffering a hand injury mid-fight, was making just his second appearance at light heavyweight.
By the halfway stage, the underdog had made it competitive, creating difficulties for Buatsi, who worked behind a solid defense to edge the better periods.
The audience's tolerance diminished amid constant clinching, with the challenger falling to the floor multiple occasions during close exchanges.
Parker finished the stronger, but many rounds were challenging to assess. Although, previous titleholder the boxing analyst - providing analysis for Dazn - had it strongly leaning for Parker, scoring for Buatsi just a single round.
Buatsi moves on, but with the likes of heavy hitter David Benavidez, and Russian champion Bivol ruling the division, the path to championship success - judging by this showing - still seems difficult.
Ricky Hatton Homage Fuels All-Manchester Contest
In the supporting bout, Arthur overcame Rea by divided decision in a terrific Manchester vs Manchester fight to capture the European light heavyweight championship.
The venue grew hushed for a deeply poignant memorial before the fight as ten bells tolled in remembrance of the city's native Hatton, who died 46 years old in September.
It was the first major televised boxing event in the urban center since the passing of Hatton. As the last bell ended, the silence became a shout of "there's only one Hatton".
The fighting during the bout reflected the sentiment. Arthur was floored by a powerful punch directly to the jaw in the second round, getting up unsteadily to his feet on the referee's count.
But the traditional red attire of the fighter soon came forward again. On the opposite side, Rea - in competitive blue - was marked up early, noticeable damage appearing under his eye as the pair exchanged hard punches.
The challenger, twenty-seven, landed power punches but the champion, 34, fought fire with fire with stinging uppercuts as the pace seldom decreased over 12 rounds.
The victor narrowly won the decision with official scores of even score, narrow lead and wider gap, but the two athletes were relentless and brave, all the qualities their inspiration Hatton represented.
