UK light heavyweight Buatsi made a winning yet underwhelming beginning to life under new promoters with a decision win over Zach Parker in the Manchester arena.
The Olympic medal winner's activity level appeared to earn him a majority decision in a close 10-round fight at the boxing arena.
But Parker had his moments, connecting with powerful single shots in a contest where the styles failed to mesh, with excessive holding marring the contest.
The scoring judges scored it 96-94 in favor to Buatsi, with the third a 95-95.
"It wasn't my best performance but what defines champions? They prevail," Buatsi said in the ring as he was faced boos from the spectators.
The British fighter got back to winning after his first professional defeat - an memorable fight with his previous opponent in last winter - to secure a 20th pro success.
Some ringside observers felt the challenger, thirty-one, merited the decision but the British boxer endured the second loss of his 28-match professional journey.
The Champion Claims Win in Dull Match
Buatsi's progress has plateaued in the past few years through contract problems and long spells of inactivity.
Once tipped as the future of British boxing, he now stands trying to fulfil that early promise - possibly in what appears to be a last chance - under fresh management.
He started carefully, with both competitors willing to take risks in a cagey initial rounds.
Parker, whose sole prior loss 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 fight at light heavyweight.
By the fight's midpoint, Parker had kept it close, creating difficulties for the favorite, who operated with a tight guard to narrowly win the cleaner periods.
The spectators' acceptance decreased during frequent holding, with the challenger falling to the floor multiple occasions during close exchanges.
The underdog ended stronger, but multiple periods were hard to judge. Nevertheless, previous titleholder Carl Frampton - commentating on Dazn - had it significantly in favor for the challenger, scoring for Buatsi just one round.
The victor progresses, but with the presence of heavy hitter Benavidez, and Russian champion Bivol ruling the division, the journey to titles - based on this performance - still looks steep.
Ricky Hatton Homage Inspires All-Manchester Contest
In the supporting bout, Arthur overcame Bradley Rea by split-decision in a terrific Manchester vs Manchester battle to secure the continental belt.
The stadium grew hushed for a deeply poignant memorial prior to the bout as a bell ceremony tolled in memory of local hero Ricky Hatton, who died aged 46 in September.
It was the first major televised match card in the city since the passing of Hatton. As the last bell disappeared, the silence transitioned to a shout of "there's only one Hatton".
The fighting inside the ropes matched the emotion. Arthur was knocked down by a powerful punch flush on the jaw in the initial stage, standing uncertainly to his footing on the eight count.
But the traditional red attire of the fighter soon advanced again. Across the ring, the opponent - in opposing blue - was injured soon, noticeable damage developing under his eye as the pair landed powerful shots.
The challenger, 27, delivered effective strikes but Arthur, thirty-four, responded in kind with stinging uppercuts as the action seldom decreased over twelve rounds.
Arthur edged the verdict with official scores of draw, narrow lead and clearer margin, but each competitor were relentless and brave, exactly what their idol Hatton represented.
