UK light heavyweight Buatsi secured a victory yet underwhelming start to life under new promoters with a decision win over Zach Parker in Manchester.
The Olympic medal winner's activity level seemingly secured him a judges' verdict in a tight 10-round fight at the boxing arena.
But the challenger had his moments, delivering effective individual punches in a match where the styles didn't complement each other, with frequent clinching marring the contest.
The scoring judges scored it 96-94 for to Buatsi, with the third a 95-95.
"It wasn't my finest display but what defines champions? They win," the victor commented in the arena as he was met by boos from the audience.
The Londoner got back to winning after his first professional defeat - an epic battle with Callum Smith in February - to claim a 20th pro success.
Several boxing experts thought the challenger, 31, merited the decision but the contender suffered the second loss of his 28-fight career.
The Champion Secures Victory in Dull Affair
The fighter's advancement has plateaued in the past few years through promotional disputes and long spells of inactivity.
Once tipped as the future of UK boxing, he now stands trying to fulfil that early promise - perhaps in what appears to be a last chance - under recent support.
He opened tentatively, with neither fighter willing to take risks in a calculated early stages.
The challenger, whose only previous defeat came at the lower weight class against his former opponent in 2022 after suffering a hand injury in the contest, was making just his second fight at light heavyweight.
By the middle rounds, the underdog had kept it close, making life awkward for Buatsi, who utilized a tight guard to narrowly win the cleaner periods.
The audience's tolerance decreased amid regular grabbing, with the challenger going down several times during clinches.
The underdog closed well, but several stanzas were challenging to assess. However, previous titleholder Carl Frampton - providing analysis for Dazn - had it strongly leaning for Parker, giving Buatsi just only one stanza.
The victor advances, but with the caliber of power puncher Benavidez, and Russian star Dmitry Bivol dominating the weight class, the road to world glory - judging by this showing - still looks steep.
Hatton Homage Inspires Manchester Derby Contest
In the secondary fight, Lyndon Arthur defeated Bradley Rea by split-decision in a outstanding all-Manchester battle to capture the continental belt.
The venue grew hushed for a profoundly moving memorial prior to the bout as a bell ceremony tolled in honor of local hero Ricky Hatton, who passed away aged 46 in recently.
It was the premier televised fight night in the urban center since the passing of Hatton. As the final chime faded, the silence transitioned to a roar of "there's just one Hatton".
The fighting inside the ropes matched the feeling. The eventual winner was floored by a powerful punch flush on the chin in the initial stage, rising shakily to his position on the referee's count.
But the red-colored attire of the fighter soon came forward again. Across the ring, the opponent - in competitive blue - was marked up quickly, heavy swelling appearing under his face as the duo landed punishing blows.
The challenger, twenty-seven, delivered effective strikes but Arthur, 34, fought fire with fire with powerful upward punches as the pace rarely dropped over twelve rounds.
Arthur edged the result with scoring tallies of 114-114, 115-113 and wider gap, but each competitor were determined and brave, exactly what their inspiration the legend embodied.
