UK light-heavyweight Buatsi earned a win yet disappointing debut to life under fresh promotional backing with a points victory over Zach Parker in the Manchester arena.
The Olympic medal winner's punch output seemingly secured him a split decision in a close 10-round contest at the Manchester venue.
But the challenger found success, delivering effective clean blows in a match where the approaches didn't complement each other, with excessive holding spoiling the fight.
The scoring judges had it 96-94 for to the winner, with the final judge a 95-95.
"It wasn't my best display but what do champions do? They win," the victor commented in the arena as he was faced negative reactions from the audience.
The Londoner bounced back after his maiden career setback - an thrilling contest with Callum Smith in February - to secure a twentieth professional win.
Several boxing experts believed the challenger, thirty-one, merited the win but the British boxer endured the second loss of his 28-match career.
Buatsi Secures Victory in Uneventful Match
The fighter's advancement has slowed in recent years through promotional disputes and extended periods of inactivity.
Previously predicted as the rising talent of British boxing, he now finds himself trying to realize his potential - maybe in what feels like a ultimate opportunity - under recent support.
He started carefully, with neither fighter ready to be aggressive in a cagey initial rounds.
The challenger, whose sole prior loss came at super middleweight against John Ryder in 2022 after damaging his hand during the bout, was making just his second fight at light heavyweight.
By the halfway stage, Parker had made it competitive, making life awkward for the favorite, who worked behind a solid defense to narrowly win the more effective periods.
The audience's tolerance wore thin amid constant clinching, with the challenger going down multiple occasions during clinches.
The underdog closed well, but multiple periods were hard to judge. Nevertheless, previous titleholder the boxing analyst - providing analysis for the broadcast network - had it strongly leaning for the challenger, awarding Buatsi just one round.
Buatsi advances, but with the presence of heavy hitter Benavidez, and Russian star Dmitry Bivol ruling the division, the journey to titles - based on this performance - still looks steep.
Hatton Memorial Motivates All-Manchester Fight
In the supporting bout, Arthur defeated Rea by split-decision in a excellent all-Manchester fight to capture the European light heavyweight belt.
The arena fell silent for a profoundly moving homage ahead of the contest as ten bells sounded in memory of Manchester's own Hatton, who passed away 46 years old in last month.
It was the premier televised fight night in the city since the passing of Hatton. As the last bell disappeared, the stillness became a roar of "there's only one Hatton".
The fighting within the ring matched the emotion. The eventual winner was knocked down by a powerful punch squarely on the chin in the initial stage, getting up unsteadily to his position on the eight count.
But the traditional red equipment of the fighter soon pressed ahead again. From the other corner, Rea - in opposing blue - was damaged quickly, noticeable damage developing under his orbital area as the fighters landed hard punches.
Rea, 27, delivered effective strikes but Arthur, 34, matched the intensity with effective uppercuts as the intensity rarely dropped over 12 rounds.
The victor narrowly won the decision with scoring tallies of 114-114, 115-113 and wider gap, but both fighters were relentless and courageous, exactly what their idol Hatton represented.
