UK light-heavyweight Buatsi made a winning yet underwhelming debut to his career under new promoters with a points victory over Zach Parker in Manchester.
The Olympic medal winner's work rate likely gained him a split decision in a close 10-round fight at the boxing arena.
But Parker landed significant shots, connecting with powerful single shots in a match where the techniques never quite clicked, with excessive holding marring the action.
The scoring judges judged it 96-94 in favor to the winner, with the remaining official a even score.
"It wasn't my best display but what defines champions? They win," the victor commented in the ring as he was met by negative reactions from the audience.
The British fighter returned to winning ways after his maiden career setback - an thrilling contest with his previous opponent in February - to claim a 20th pro success.
Various analysts felt the challenger, thirty-one, should have been awarded the decision but the contender endured the second setback of his 28-bout professional journey.
The Champion Secures Victory in Slow Match
His career development has slowed in the past few years through management issues and long spells of lack of fights.
Previously predicted as the future of British boxing, he now stands trying to realize his potential - maybe in what feels like a final roll of the dice - under fresh management.
He began cautiously, with the two boxers ready to be aggressive in a cagey opening few rounds.
The challenger, whose only previous defeat came at the lower weight class against John Ryder in two years ago after suffering a hand injury in the contest, was participating in his second appearance at light heavyweight.
By the halfway stage, the underdog had stayed in contention, making life awkward for the favorite, who worked behind a solid defense to barely take the more effective periods.
The audience's tolerance decreased during regular grabbing, with Parker going down multiple occasions during clinches.
The underdog ended stronger, but many rounds were challenging to assess. However, previous titleholder the boxing analyst - working with the broadcast network - had it significantly in favor for Parker, scoring for Buatsi just only one stanza.
The victor moves on, but with the caliber of power puncher David Benavidez, and Russian star Bivol dominating the weight class, the path to championship success - judging by this showing - still appears challenging.
Hatton Memorial Inspires All-Manchester Fight
In the co-main event, Lyndon Arthur defeated Rea by close verdict in a outstanding local rivalry contest to secure the continental title.
The stadium grew hushed for a extremely emotional tribute prior to the bout as 10 bells rang in remembrance of local hero Hatton, who succumbed aged 46 in September.
It was the initial significant broadcast fight night in the urban center since Hatton's death. As the concluding sound disappeared, the stillness gave way to a chant of "only one Ricky Hatton".
The fighting inside the ropes matched the sentiment. The eventual winner was floored by a powerful punch directly to the face in the early round, standing uncertainly to his position on the count of eight.
But the traditional red shorts of the fighter soon advanced again. From the other corner, Rea - in competitive blue - was damaged early, noticeable damage appearing under his face as the fighters traded hard punches.
The challenger, 27, landed power punches but Arthur, thirty-four, responded in kind with effective uppercuts as the action hardly diminished over the full distance.
The victor edged the verdict with official scores of even score, close margin and clearer margin, but both fighters were relentless and full of heart, everything their idol the legend stood for.
