UK light heavyweight Buatsi made a winning yet disappointing beginning to life under recent management with a unanimous decision over Zach Parker in the Manchester arena.
The Olympic medal winner's work rate likely gained him a judges' verdict in a tight 10-round bout at the Manchester venue.
But Parker landed significant shots, landing some telling single shots in a match where the styles never quite clicked, with constant grabbing spoiling the fight.
Two judges judged it 96-94 for to Buatsi, with the final judge a even score.
"It wasn't my best display but how do champions respond? They succeed," the victor commented in the arena as he was greeted with boos from the audience.
The British fighter got back to winning after his initial pro loss - an thrilling contest with Callum Smith in last winter - to secure a 20th pro success.
Several boxing experts thought the challenger, thirty-one, deserved the decision but the contender experienced the second setback of his 28-match professional journey.
Buatsi Secures Win in Slow Match
Buatsi's progress has stalled in recent years through promotional disputes and extended periods of inactivity.
Once tipped as the rising talent of British boxing, he now finds himself trying to achieve expectations - perhaps in what feels like a last chance - under new promotional backing.
He opened tentatively, with neither fighter willing to overcommit in a cagey early stages.
The challenger, whose single earlier setback came at super middleweight against his former opponent in two years ago after suffering a hand injury in the contest, was making just his second fight at light-heavyweight.
By the halfway stage, the underdog had stayed in contention, creating difficulties for Buatsi, who worked behind a solid defense to narrowly win the more effective periods.
The audience's tolerance decreased because of frequent holding, with the challenger slipping to the canvas multiple occasions during grappling.
Parker ended stronger, but multiple periods were hard to judge. Nevertheless, previous titleholder the boxing analyst - commentating on the broadcast network - had it strongly leaning for the challenger, scoring for Buatsi just a single round.
Buatsi progresses, but with the caliber of power puncher David Benavidez, and Eastern European fighter Dmitry Bivol leading the category, the path to championship success - on this evidence - still appears challenging.
Ricky Hatton Tribute Fuels All-Manchester Fight
In the supporting bout, Lyndon Arthur defeated Rea by close verdict in a excellent all-Manchester battle to capture the European light heavyweight belt.
The venue fell silent for a profoundly moving homage before the fight as 10 bells tolled in memory of Manchester's own Ricky Hatton, who died 46 years old in September.
It was the initial significant broadcast boxing event in the urban center since Hatton's passing. As the concluding sound faded, the quiet transitioned to a shout of "there's only one Hatton".
The fighting during the bout reflected the emotion. The eventual winner was floored by a powerful punch flush on the chin in the initial stage, standing uncertainly to his footing on the eight count.
But the red-colored attire of Arthur soon came forward again. From the other corner, Rea - in competitive blue - was damaged quickly, significant bruising appearing under his face as the duo traded punishing blows.
Rea, twenty-seven, landed power punches but Arthur, 34, responded in kind with stinging uppercuts as the action hardly diminished over the full distance.
The victor barely secured the verdict with official scores of draw, narrow lead and clearer margin, but the two athletes were determined and brave, exactly what their idol the legend represented.
