UK light-heavyweight Buatsi earned a win yet disappointing start to his career under new promoters with a unanimous decision over Zach Parker in Manchester.
The Olympic medal winner's activity level appeared to earn him a majority decision in a close 10-round fight at the boxing arena.
But Parker landed significant shots, connecting with powerful individual punches in a fight where the approaches never quite clicked, with constant grabbing marring the contest.
The officials had it 96-94 in favor to Buatsi, with the third a 95-95 draw.
"It wasn't my finest performance but what defines champions? They prevail," the victor said in the ringside as he was greeted with boos from the crowd.
The Londoner got back to winning after his maiden career setback - an epic battle with Callum Smith in February - to claim a 20th career victory.
Various analysts thought the challenger, thirty-one, should have been awarded the decision but the British boxer suffered the second defeat of his 28-fight career.
Buatsi Claims Triumph in Dull Affair
The fighter's advancement has plateaued in recent times through management issues and long spells of inactivity.
Earlier forecast as the next star of the British fight scene, he now is positioned trying to fulfil that early promise - maybe in what feels like a last chance - under fresh management.
He began cautiously, with both competitors willing to overcommit in a tentative initial rounds.
The challenger, whose sole prior loss came at super-middleweight against his former opponent in two years ago after suffering a hand injury during the bout, was competing in only his second fight at light heavyweight.
By the fight's midpoint, Parker had made it competitive, causing problems for Buatsi, who utilized a solid defense to edge the better rounds.
The audience's tolerance diminished amid regular grabbing, with the challenger slipping to the canvas various instances during close exchanges.
Parker finished the stronger, but many rounds were challenging to assess. Nevertheless, previous titleholder the boxing analyst - working with Dazn - had it significantly in favor for Parker, awarding Buatsi just a single round.
Buatsi advances, but with the likes of hard hitter Benavidez, and Russian star Bivol leading the category, the road to world glory - judging by this showing - still appears challenging.
Hatton Memorial Fuels Local Rivalry Fight
In the secondary fight, Arthur beat Rea by divided decision in a outstanding local rivalry contest to capture the European light-heavyweight belt.
The stadium became quiet for a deeply poignant tribute prior to the bout as ten bells sounded in honor of the city's native Hatton, who died aged 46 in recently.
It was the first major televised match card in the location since the passing of Hatton. As the concluding sound faded, the stillness transitioned to a chant of "only one Ricky Hatton".
The competition inside the ropes matched the feeling. Arthur was knocked down by a left hook squarely on the face in the early round, standing uncertainly to his feet on the count of eight.
But the traditional red attire of Arthur soon pressed ahead again. On the opposite side, the opponent - in rival City blue - was marked up soon, significant bruising forming under his eye as the duo traded powerful shots.
The challenger, 27, delivered effective strikes but Arthur, thirty-four, fought fire with fire with powerful upward punches as the intensity rarely dropped over twelve rounds.
Arthur barely secured the result with judges scorecards of draw, close margin and clearer margin, but both fighters were persistent and full of heart, everything their hero Hatton stood for.
