British light-heavyweight Buatsi made a winning yet underwhelming start to life under fresh promotional backing with a points victory over Zach Parker in Manchester.
The Olympic bronze medallist's punch output seemingly secured him a split decision in a tight ten-round bout at the boxing arena.
But Parker landed significant shots, landing some telling clean blows in a fight where the styles never quite clicked, with frequent clinching marring the contest.
Two judges judged it 96-94 to Buatsi, with the third a 95-95.
"It wasn't my greatest performance but what defines champions? They win," the victor said in the arena as he was faced disapproval from the spectators.
The Londoner returned to winning ways after his initial pro loss - an epic battle with Callum Smith in February - to claim a 20th career victory.
Several boxing experts felt the challenger, 31, should have been awarded the decision but the Derbyshire fighter endured the second loss of his 28-match career.
The Champion Claims Triumph in Slow Encounter
Buatsi's progress has slowed in recent times through management issues and long spells of inactivity.
Earlier forecast as the future of the British fight scene, he now stands trying to achieve expectations - maybe in what appears to be a final roll of the dice - under new promotional backing.
He started carefully, with neither fighter ready to be aggressive in a tentative initial rounds.
The challenger, whose single earlier setback came at the lower weight class against his former opponent in 2022 after suffering a hand injury during the bout, was competing in only his second fight at the higher weight class.
By the middle rounds, Parker had kept it close, creating difficulties for the favorite, who operated with a tight guard to narrowly win the cleaner periods.
The crowd's patience decreased because of frequent holding, with Parker going down several times during clinches.
Parker ended stronger, but several stanzas were difficult to score. Although, previous titleholder Carl Frampton - commentating on Dazn - had it particularly wide for Parker, giving Buatsi just one round.
The victor progresses, but with the caliber of hard hitter Benavidez, and Russian champion Dmitry Bivol ruling the division, the journey to titles - judging by this showing - still appears challenging.
Hatton Homage Fuels Manchester Derby Contest
In the supporting bout, Arthur overcame Bradley Rea by divided decision in a excellent Manchester vs Manchester battle to secure the European light-heavyweight title.
The arena grew hushed for a deeply poignant memorial ahead of the contest as 10 bells rang in memory of Manchester's own Ricky Hatton, who died 46 years old in recently.
It was the first major televised boxing event in the city since the passing of Hatton. As the concluding sound faded, the silence transitioned to a roar of "there's only one Hatton".
The competition within the ring equaled the sentiment. The eventual winner was knocked down by a powerful punch directly to the jaw in the initial stage, rising shakily to his footing on the count of eight.
But the traditional red shorts of Arthur soon pressed ahead again. From the other corner, the opponent - in rival City blue - was injured soon, significant bruising appearing under his face as the fighters landed powerful shots.
The challenger, twenty-seven, delivered effective strikes but the champion, 34, fought fire with fire with stinging uppercuts as the pace hardly diminished over 12 rounds.
Arthur barely secured the result with scoring tallies of even score, close margin and clearer margin, but both fighters were persistent and courageous, everything their idol the legend represented.
