UK light heavyweight Buatsi made a winning yet disappointing beginning to his career under new promoters with a points victory over Zach Parker in Manchester.
The Olympic bronze medallist's work rate seemingly secured him a split decision in a tight ten-round bout at the Co-op Live Arena.
But Parker landed significant shots, landing some telling individual punches in a match where the techniques didn't complement each other, with frequent clinching spoiling the action.
Two judges had it 96-94 for to the winner, with the final judge a 95-95 draw.
"It wasn't my greatest display but what defines champions? They prevail," the victor said in the ringside as he was greeted with boos from the spectators.
The British fighter got back to winning after his maiden career setback - an memorable fight with Callum Smith in February - to secure a twentieth professional win.
Various analysts felt Parker, thirty-one, deserved the victory but the Derbyshire fighter suffered the second defeat of his 28-fight career.
The Champion Claims Win in Dull Match
The fighter's advancement has stalled in recent years through promotional disputes and considerable time of inactivity.
Earlier forecast as the rising talent of the British fight scene, he now stands trying to achieve expectations - possibly in what feels like a ultimate opportunity - under new promotional backing.
He opened tentatively, with both competitors willing to overcommit in a calculated early stages.
The challenger, whose sole prior loss came at super-middleweight against John Ryder in two years ago after suffering a hand injury in the contest, was making just his second appearance at light-heavyweight.
By the fight's midpoint, Parker had made it competitive, creating difficulties for the favorite, who operated with a protective stance to narrowly win the more effective stanzas.
The spectators' acceptance wore thin amid regular grabbing, with the challenger slipping to the canvas multiple occasions during grappling.
The underdog finished the stronger, but multiple periods were challenging to assess. Although, previous titleholder the boxing analyst - commentating on Dazn - had it particularly wide for Parker, scoring for Buatsi just only one stanza.
The victor advances, but with the presence of power puncher David Benavidez, and Russian star Dmitry Bivol dominating the weight class, the path to championship success - based on this performance - still looks steep.
Hatton Memorial Motivates Local Rivalry Battle
In the co-main event, Arthur defeated Bradley Rea by close verdict in a terrific all-Manchester contest to win the continental championship.
The arena grew hushed for a extremely emotional memorial ahead of the contest as ten bells tolled in honor of local hero Hatton, who passed away 46 years old in last month.
It was the premier televised match card in the location since Hatton's death. As the last bell disappeared, the silence gave way to a chant of "there's just one Ricky Hatton".
The action within the ring equaled the feeling. Arthur was floored by a powerful punch flush on the jaw in the initial stage, standing uncertainly to his footing on the referee's count.
But the Manchester United-red shorts of the fighter soon advanced again. Across the ring, Rea - in rival City blue - was injured soon, heavy swelling appearing under his face as the duo exchanged hard punches.
Rea, twenty-seven, delivered effective strikes but the champion, 34, fought fire with fire with powerful upward punches as the intensity hardly diminished over 12 rounds.
Arthur barely secured the decision with judges scorecards of even score, narrow lead and 115-112, but the two athletes were determined and full of heart, all the qualities their inspiration Hatton embodied.
