UK light heavyweight Buatsi earned a win yet disappointing beginning to life under fresh promotional backing with a unanimous decision over Zach Parker in the Manchester arena.
The Olympic medal winner's activity level appeared to earn him a judges' verdict in a close 10-round bout at the boxing arena.
But Parker landed significant shots, connecting with powerful clean blows in a match where the styles failed to mesh, with frequent clinching marring the fight.
Two judges had it 96-94 in favor to the winner, with the final judge a even score.
"It wasn't my greatest display but what defines champions? They win," Buatsi said in the ringside as he was greeted with boos from the spectators.
The British fighter returned to winning ways after his maiden career setback - an memorable fight with his previous opponent in February - to secure a 20th career victory.
Various analysts thought Parker, thirty-one, merited the victory but the Derbyshire fighter suffered the second loss of his 28-fight career.
Buatsi Earns Victory in Slow Match
His career development has plateaued in recent times through promotional disputes and extended periods of inactivity.
Previously predicted as the next star of British boxing, he now stands trying to realize his potential - maybe in what seems like a last chance - under fresh management.
He started carefully, with both competitors prepared to overcommit in a cagey early stages.
Parker, whose single earlier setback came at super-middleweight against John Ryder in 2022 after suffering a hand injury mid-fight, was competing in only his second fight at light-heavyweight.
By the halfway stage, Parker had stayed in contention, causing problems for the favorite, who worked behind a protective stance to barely take the better rounds.
The crowd's patience decreased during regular grabbing, with the challenger going down various instances during close exchanges.
The underdog closed well, but several stanzas were challenging to assess. Although, ex-champion the boxing analyst - providing analysis for the broadcast network - had it strongly leaning for Parker, awarding Buatsi just a single round.
Buatsi moves on, but with the likes of power puncher David Benavidez, and Russian champion Dmitry Bivol ruling the division, the journey to titles - judging by this showing - still seems difficult.
Hatton Memorial Motivates Local Rivalry Contest
In the co-main event, Arthur beat Rea by divided decision in a outstanding all-Manchester battle to secure the European light heavyweight championship.
The venue became quiet for a deeply poignant homage ahead of the contest as a bell ceremony rang in memory of the city's native Ricky Hatton, who died 46 years old in September.
It was the premier televised fight night in the city since Hatton's passing. As the last bell faded, the quiet transitioned to a shout of "only one Hatton".
The fighting inside the ropes matched the emotion. The eventual winner was knocked down by a powerful punch flush on the jaw in the early round, standing uncertainly to his footing on the count of eight.
But the traditional red attire of Arthur soon advanced again. Across the ring, Rea - in competitive blue - was injured early, significant bruising forming under his face as the fighters exchanged powerful shots.
The challenger, twenty-seven, landed power punches but the champion, 34, responded in kind with powerful upward punches as the pace hardly diminished over 12 rounds.
The victor barely secured the verdict with judges scorecards of draw, 115-113 and wider gap, but the two athletes were determined and full of heart, everything their hero Hatton represented.
