UK light heavyweight Buatsi made a winning yet unimpressive debut to his career under recent management with a unanimous decision over Zach Parker in Manchester.
The Olympic bronze medallist's punch output likely gained him a split decision in a close ten-round bout at the Co-op Live Arena.
But Parker landed significant shots, delivering effective individual punches in a contest where the approaches never quite clicked, with excessive holding spoiling the contest.
Two judges had it 96-94 in favor to the winner, with the remaining official a even score.
"It wasn't my finest performance but what do champions do? They prevail," the victor stated in the arena as he was greeted with negative reactions from the spectators.
The Londoner bounced back after his initial pro loss - an epic battle with Callum Smith in February - to claim a 20th pro success.
Various analysts thought the challenger, thirty-one, deserved the decision but the British boxer experienced the second defeat of his 28-match career.
The Champion Claims Victory in Uneventful Match
His career development has slowed in recent times through management issues and long spells of inactivity.
Earlier forecast as the rising talent of the British fight scene, he now finds himself trying to fulfil that early promise - maybe in what appears to be a final roll of the dice - under new promotional backing.
He started carefully, with the two boxers willing to take risks in a tentative initial rounds.
The challenger, whose only previous defeat came at super-middleweight against his former opponent in 2022 after breaking his hand in the contest, was competing in only his second fight at light heavyweight.
By the halfway stage, Parker had kept it close, making life awkward for the favorite, who utilized a tight guard to barely take the cleaner stanzas.
The spectators' acceptance decreased during constant clinching, with Parker falling to the floor several times during clinches.
Parker ended stronger, but multiple periods were difficult to score. However, ex-champion Carl Frampton - working with Dazn - had it particularly wide for the challenger, giving Buatsi just a single round.
Buatsi moves on, but with the presence of power puncher Benavidez, and Eastern European fighter Bivol dominating the weight class, the road to world glory - based on this performance - still looks steep.
Ricky Hatton Memorial Motivates Manchester Derby Contest
In the co-main event, Arthur defeated Bradley Rea by divided decision in a terrific all-Manchester contest to win the European light heavyweight title.
The stadium became quiet for a extremely emotional homage prior to the bout as 10 bells sounded in memory of Manchester's own Hatton, who died at age 46 in September.
It was the premier televised fight night in the city since the passing of Hatton. As the last bell faded, the quiet transitioned to a shout of "there's just one Ricky Hatton".
The competition during the bout equaled the emotion. Arthur was floored by a significant blow squarely on the jaw in the initial stage, rising shakily to his footing on the eight count.
But the red-colored shorts of the fighter soon pressed ahead again. From the other corner, Rea - in competitive blue - was damaged quickly, heavy swelling appearing under his orbital area as the duo landed hard punches.
The challenger, 27, delivered effective strikes but Arthur, thirty-four, fought fire with fire with powerful upward punches as the intensity rarely dropped over the full distance.
Arthur narrowly won the verdict with official scores of even score, narrow lead and clearer margin, but each competitor were relentless and full of heart, exactly what their idol the legend stood for.
