British light-heavyweight Buatsi secured a victory yet unimpressive start to life under new promoters with a decision win over Zach Parker in the Manchester arena.
The Olympic medal winner's work rate seemingly secured him a judges' verdict in a tight ten-round bout at the boxing arena.
But Parker found success, landing some telling clean blows in a contest where the styles failed to mesh, with constant grabbing spoiling the contest.
The officials judged it 96-94 to Buatsi, with the final judge a 95-95.
"It wasn't my finest showing but what do champions do? They prevail," the victor said in the ring as he was greeted with disapproval from the crowd.
The Londoner bounced back after his maiden career setback - an thrilling contest with Callum Smith in last winter - to earn a 20th pro success.
Some ringside observers believed Parker, 31, should have been awarded the win but the Derbyshire fighter endured the second setback of his 28-fight career.
Buatsi Secures Win in Uneventful Encounter
His career development has slowed in the past few years through management issues and long spells of lack of fights.
Previously predicted as the future of the British fight scene, he now stands trying to achieve expectations - perhaps in what feels like a final roll of the dice - under recent support.
He began cautiously, with neither fighter ready to take risks in a cagey initial rounds.
The challenger, whose single earlier setback came at super-middleweight against John Ryder in 2022 after suffering a hand injury mid-fight, was making just his second appearance at the higher weight class.
By the halfway stage, Parker had made it competitive, making life awkward for the favorite, who operated with a tight guard to barely take the cleaner periods.
The crowd's patience decreased amid regular grabbing, with Parker going down several times during grappling.
Parker ended stronger, but many rounds were difficult to score. Nevertheless, previous titleholder the boxing analyst - commentating on Dazn - had it particularly wide for the challenger, awarding Buatsi just one round.
The victor moves on, but with the presence of heavy hitter Benavidez, and Eastern European fighter Dmitry Bivol ruling the division, the path to championship success - judging by this showing - still appears challenging.
Hatton Tribute Fuels Local Rivalry Contest
In the supporting bout, Arthur beat Rea by close verdict in a excellent all-Manchester battle to secure the continental championship.
The stadium became quiet for a profoundly moving memorial prior to the bout as a bell ceremony tolled in honor of local hero Ricky Hatton, who succumbed at age 46 in September.
It was the initial significant broadcast boxing event in the location since Hatton's death. As the final chime disappeared, the quiet gave way to a roar of "there's only one Hatton".
The fighting within the ring equaled the feeling. The eventual winner was sent to the canvas by a significant blow directly to the face in the early round, rising shakily to his footing on the referee's count.
But the red-colored shorts of the fighter soon advanced again. Across the ring, Rea - in rival City blue - was damaged quickly, significant bruising appearing under his eye as the pair landed punishing blows.
The challenger, 27, delivered effective strikes but the champion, 34, responded in kind with effective uppercuts as the action hardly diminished over 12 rounds.
Arthur edged the decision with scoring tallies of draw, narrow lead and wider gap, but each competitor were persistent and full of heart, exactly what their inspiration Hatton embodied.
