British light-heavyweight Buatsi secured a victory yet disappointing debut to life under recent management with a decision win over Zach Parker in the Manchester arena.
The Olympic medal winner's work rate likely gained him a judges' verdict in a close 10-round contest at the Manchester venue.
But Parker found success, connecting with powerful single shots in a match where the approaches failed to mesh, with excessive holding disrupting the fight.
Two judges scored it 96-94 for to the winner, with the final judge a even score.
"It wasn't my finest showing but how do champions respond? They win," Buatsi said in the arena as he was faced boos from the audience.
The Londoner got back to winning after his first professional defeat - an memorable fight with Callum Smith in last winter - to claim a 20th pro success.
Several boxing experts thought the challenger, thirty-one, merited the decision but the contender experienced the second defeat of his 28-fight professional journey.
The Champion Secures Victory in Slow Affair
His career development has slowed in recent times through management issues and long spells of inactivity.
Once tipped as the rising talent of the British fight scene, he now stands trying to realize his potential - possibly in what appears to be a ultimate opportunity - under fresh management.
He started carefully, with both competitors ready to overcommit in a tentative initial rounds.
Parker, whose only previous defeat came at super-middleweight against his former opponent in two years ago after suffering a hand injury during the bout, was making just his second bout at the higher weight class.
By the halfway stage, the underdog had made it competitive, creating difficulties for the favorite, who operated with a solid defense to barely take the cleaner periods.
The crowd's patience wore thin during frequent holding, with the challenger falling to the floor several times during clinches.
Parker ended stronger, but multiple periods were difficult to score. Although, previous titleholder Carl Frampton - commentating on the broadcast network - had it strongly leaning for the challenger, scoring for Buatsi just a single round.
Buatsi advances, but with the likes of heavy hitter Benavidez, and Russian star Dmitry Bivol dominating the weight class, the path to championship success - based on this performance - still looks steep.
Hatton Memorial Inspires Manchester Derby Fight
In the supporting bout, Arthur defeated Rea by divided decision in a excellent local rivalry contest to capture the continental title.
The venue fell silent for a profoundly moving memorial prior to the bout as a bell ceremony sounded in honor of Manchester's own Hatton, who died aged 46 in last month.
It was the premier televised match card in the urban center since the passing of Hatton. As the final chime ended, the quiet became a chant of "there's only one Hatton".
The fighting within the ring matched the emotion. The eventual winner was floored by a significant blow squarely on the face in the second round, standing uncertainly to his footing on the count of eight.
But the traditional red equipment of Arthur soon came forward again. From the other corner, the opponent - in opposing blue - was injured early, heavy swelling forming under his eye as the fighters traded powerful shots.
Rea, twenty-seven, delivered effective strikes but the champion, 34, responded in kind with powerful upward punches as the pace seldom decreased over twelve rounds.
Arthur narrowly won the verdict with judges scorecards of 114-114, close margin and wider gap, but both fighters were determined and full of heart, all the qualities their inspiration the legend embodied.
