UK light-heavyweight Buatsi earned a win yet disappointing start to life under new promoters with a unanimous decision over Zach Parker in Manchester.
The Olympic bronze medallist's activity level appeared to earn him a judges' verdict in a close 10-round bout at the Manchester venue.
But the challenger landed significant shots, connecting with powerful individual punches in a contest where the techniques failed to mesh, with excessive holding disrupting the fight.
The scoring judges judged it 96-94 for to the winner, with the third a 95-95.
"It wasn't my best display but what defines champions? They prevail," the victor said in the ringside as he was met by negative reactions from the crowd.
The Londoner got back to winning after his first professional defeat - an thrilling contest with his previous opponent in February - to earn a twentieth professional win.
Various analysts felt the challenger, 31, deserved the victory but the Derbyshire fighter suffered the second setback of his 28-match career.
The Champion Earns Triumph in Uneventful Encounter
The fighter's advancement has stalled in recent years through contract problems and extended periods of inactivity.
Earlier forecast as the rising talent of the British fight scene, he now finds himself trying to achieve expectations - possibly in what appears to be a ultimate opportunity - under fresh management.
He opened tentatively, with the two boxers willing to be aggressive in a cagey initial rounds.
The challenger, whose only previous defeat came at the lower weight class against John Ryder in 2022 after damaging his hand mid-fight, was participating in his second fight at light heavyweight.
By the fight's midpoint, Parker had stayed in contention, causing problems for Buatsi, who operated with a tight guard to narrowly win the cleaner stanzas.
The audience's tolerance diminished amid frequent holding, with Parker slipping to the canvas several times during grappling.
The underdog finished the stronger, but multiple periods were difficult to score. Nevertheless, ex-champion the boxing analyst - working with the broadcast network - had it particularly wide for the challenger, giving Buatsi just a single round.
Buatsi moves on, but with the caliber of hard hitter Benavidez, and Russian star Bivol dominating the weight class, the road to world glory - based on this performance - still appears challenging.
Ricky Hatton Homage Fuels Local Rivalry Contest
In the supporting bout, Arthur defeated Rea by divided decision in a outstanding all-Manchester battle to win the continental belt.
The venue grew hushed for a extremely emotional homage before the fight as ten bells rang in memory of Manchester's own Hatton, who died at age 46 in last month.
It was the premier televised match card in the city since Hatton's passing. As the concluding sound ended, the silence transitioned to a chant of "there's just one Hatton".
The competition within the ring reflected the feeling. The eventual winner was floored by a left hook flush on the jaw in the second round, getting up unsteadily to his footing on the eight count.
But the red-colored attire of Arthur soon advanced again. From the other corner, Rea - in competitive blue - was injured early, noticeable damage developing under his face as the pair traded powerful shots.
Rea, twenty-seven, connected with strong blows but Arthur, 34, fought fire with fire with powerful upward punches as the pace hardly diminished over the full distance.
Arthur narrowly won the decision with official scores of draw, narrow lead and clearer margin, but each competitor were persistent and courageous, everything their idol the legend embodied.
