UK light-heavyweight Buatsi made a winning yet unimpressive 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 judges' verdict in a close ten-round fight at the Co-op Live Arena.
But the challenger found success, delivering effective clean blows in a contest where the techniques failed to mesh, with excessive holding spoiling the contest.
The scoring judges judged it 96-94 for to the winner, with the third a even score.
"It wasn't my greatest performance but how do champions respond? They win," Buatsi said in the ring as he was faced disapproval from the audience.
The British fighter got back to winning after his maiden career setback - an epic battle with his previous opponent in February - to earn a twentieth professional win.
Some ringside observers felt the challenger, 31, merited the win but the contender experienced the second defeat of his 28-bout career.
The Champion Claims Win in Uneventful Affair
The fighter's advancement has plateaued in recent years through management issues and considerable time of inactivity.
Earlier forecast as the rising talent of UK boxing, he now finds himself trying to achieve expectations - maybe in what feels like a last chance - under fresh management.
He opened tentatively, with both competitors prepared to overcommit in a tentative opening few rounds.
Parker, whose only previous defeat came at the lower weight class against his former opponent in two years ago after suffering a hand injury in the contest, was participating in his second bout at light heavyweight.
By the fight's midpoint, Parker had kept it close, making life awkward for the favorite, who utilized a protective stance to narrowly win the more effective rounds.
The spectators' acceptance wore thin during constant clinching, with Parker falling to the floor multiple occasions during clinches.
The underdog ended stronger, but several stanzas were difficult to score. Nevertheless, ex-champion the boxing analyst - providing analysis for Dazn - had it particularly wide for the challenger, scoring for Buatsi just a single round.
The victor moves on, but with the presence of heavy hitter Benavidez, and Eastern European fighter Dmitry Bivol leading the category, the journey to titles - on this evidence - still looks steep.
Hatton Homage Inspires All-Manchester Fight
In the secondary fight, Arthur overcame Bradley Rea by divided decision in a excellent Manchester vs Manchester battle to capture the European light heavyweight championship.
The arena became quiet for a deeply poignant memorial prior to the bout as a bell ceremony sounded in memory of Manchester's own Hatton, who succumbed aged 46 in recently.
It was the initial significant broadcast fight night in the location since Hatton's passing. As the last bell ended, the quiet transitioned to a shout of "there's just one Ricky Hatton".
The action within the ring matched the emotion. The eventual winner was knocked down by a left hook flush on the face in the second round, rising shakily to his footing on the referee's count.
But the Manchester United-red equipment of Arthur soon advanced again. From the other corner, the opponent - in rival City blue - was injured soon, noticeable damage developing under his orbital area as the pair landed powerful shots.
The challenger, 27, landed power punches but Arthur, 34, matched the intensity with stinging uppercuts as the action seldom decreased over twelve rounds.
The victor narrowly won the result with scoring tallies of 114-114, 115-113 and 115-112, but both fighters were relentless and courageous, all the qualities their inspiration Hatton embodied.
