British light heavyweight Buatsi secured a victory yet disappointing 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 appeared to earn him a majority decision in a close ten-round fight at the Co-op Live Arena.
But the challenger had his moments, landing some telling individual punches in a contest where the styles failed to mesh, with excessive holding spoiling the action.
Two judges judged it 96-94 in favor to the winner, with the third a 95-95 draw.
"It wasn't my best display but how do champions respond? They win," Buatsi stated in the arena as he was met by negative reactions from the audience.
The British fighter got back to winning after his maiden career setback - an epic battle with Callum Smith in February - to secure a 20th career victory.
Some ringside observers believed the challenger, 31, deserved the win but the Derbyshire fighter experienced the second loss of his 28-bout professional journey.
Buatsi Secures Victory in Uneventful Match
Buatsi's progress has plateaued in recent times through contract problems and considerable time of inactivity.
Once tipped as the rising talent of the British fight scene, he now is positioned trying to achieve expectations - perhaps in what appears to be a ultimate opportunity - under recent support.
He began cautiously, with both competitors willing to be aggressive in a cagey opening few rounds.
The challenger, whose only previous defeat came at super middleweight against his former opponent in two years ago after damaging his hand mid-fight, was competing in only his second bout at light-heavyweight.
By the fight's midpoint, Parker had stayed in contention, making life awkward for Buatsi, who utilized a protective stance to barely take the better periods.
The crowd's patience diminished amid regular grabbing, with the challenger going down multiple occasions during clinches.
The underdog finished the stronger, but many rounds were challenging to assess. However, previous titleholder the boxing analyst - providing analysis for the broadcast network - had it strongly leaning for the challenger, scoring for Buatsi just one round.
The victor progresses, but with the presence of hard hitter Benavidez, and Russian champion Dmitry Bivol dominating the weight class, the path to championship success - on this evidence - still seems difficult.
Hatton Memorial Inspires Manchester Derby Fight
In the supporting bout, Arthur defeated Rea by close verdict in a excellent local rivalry fight to win the continental belt.
The stadium grew hushed for a profoundly moving memorial ahead of the contest as 10 bells tolled in remembrance of Manchester's own Hatton, who died aged 46 in September.
It was the initial significant broadcast boxing event in the urban center since Hatton's death. As the final chime disappeared, the stillness gave way to a shout of "only one Ricky Hatton".
The fighting inside the ropes equaled the emotion. Arthur was sent to the canvas by a left hook flush on the face in the early round, standing uncertainly to his footing on the eight count.
But the traditional red attire of the fighter soon came forward again. From the other corner, Rea - in opposing blue - was damaged soon, heavy swelling appearing under his face as the fighters landed powerful shots.
Rea, twenty-seven, delivered effective strikes but the champion, 34, responded in kind with powerful upward punches as the intensity hardly diminished over the full distance.
The victor edged the verdict with judges scorecards of draw, 115-113 and wider gap, but the two athletes were determined and courageous, all the qualities their inspiration the legend embodied.
