UK light heavyweight Buatsi secured a victory yet underwhelming beginning to life under fresh promotional backing with a points victory over Zach Parker in the Manchester arena.
The Olympic medal winner's punch output likely gained him a split decision in a competitive ten-round bout at the Co-op Live Arena.
But the challenger landed significant shots, connecting with powerful single shots in a fight where the techniques never quite clicked, with frequent clinching disrupting the fight.
The officials had it 96-94 in favor to Buatsi, with the remaining official a 95-95 draw.
"It wasn't my best showing but what defines champions? They win," Buatsi said in the arena as he was met by negative reactions from the crowd.
The Londoner returned to winning ways after his maiden career setback - an thrilling contest with his previous opponent in February - to secure a 20th career victory.
Various analysts thought Parker, thirty-one, should have been awarded the win but the British boxer experienced the second loss of his 28-match professional journey.
Buatsi Secures Victory in Dull Affair
His career development has slowed in recent times through management issues and considerable time of lack of fights.
Once tipped as the rising talent of UK boxing, he now is positioned trying to achieve expectations - maybe in what feels like a final roll of the dice - under recent support.
He opened tentatively, with both competitors ready to overcommit in a tentative initial rounds.
The challenger, whose sole prior loss came at super-middleweight against his former opponent in two years ago after suffering a hand injury mid-fight, was participating in his second fight at light heavyweight.
By the middle rounds, the underdog had stayed in contention, making life awkward for the favorite, who operated with a tight guard to barely take the better stanzas.
The crowd's patience wore thin during constant clinching, with the challenger going down various instances during clinches.
The underdog ended stronger, but several stanzas were hard to judge. Nevertheless, former world champion Carl Frampton - commentating on Dazn - had it strongly leaning for Parker, scoring for Buatsi just only one stanza.
Buatsi progresses, but with the presence of hard hitter David Benavidez, and Eastern European fighter Bivol leading the category, the journey to titles - based on this performance - still appears challenging.
Ricky Hatton Memorial Motivates Local Rivalry Battle
In the supporting bout, Arthur overcame Rea by split-decision in a terrific all-Manchester battle to capture the European light-heavyweight championship.
The arena fell silent for a profoundly moving memorial prior to the bout as a bell ceremony sounded in memory of Manchester's own Ricky Hatton, who passed away 46 years old in September.
It was the first major televised fight night in the city since Hatton's death. As the concluding sound disappeared, the silence gave way to a chant of "there's just one Hatton".
The action within the ring equaled the sentiment. The eventual winner was sent to the canvas by a powerful punch squarely on the face in the initial stage, rising shakily to his position on the eight count.
But the red-colored attire of the fighter soon advanced again. On the opposite side, Rea - in competitive blue - was damaged quickly, heavy swelling forming under his orbital area as the pair landed punishing blows.
The challenger, twenty-seven, connected with strong blows but Arthur, 34, responded in kind with effective uppercuts as the pace hardly diminished over 12 rounds.
Arthur edged the decision with judges scorecards of even score, close margin and wider gap, but both fighters were determined and full of heart, everything their hero Hatton stood for.
