UK light-heavyweight Buatsi earned a win yet underwhelming debut to life under new promoters with a decision win over Zach Parker in Manchester.
The Olympic bronze medallist's work rate appeared to earn him a split decision in a tight 10-round fight at the Co-op Live Arena.
But Parker landed significant shots, connecting with powerful clean blows in a match where the styles didn't complement each other, with frequent clinching marring the fight.
The scoring judges scored it 96-94 in favor to the winner, with the final judge a 95-95.
"It wasn't my finest showing but what defines champions? They win," the victor stated in the arena as he was met by negative reactions from the audience.
The British fighter bounced back after his first professional defeat - an memorable fight with his previous opponent in last winter - to earn a twentieth professional win.
Several boxing experts believed the challenger, 31, should have been awarded the victory but the contender endured the second setback of his 28-fight professional journey.
Buatsi Claims Win in Uneventful Affair
Buatsi's progress has plateaued in recent times through contract problems and long spells of inactivity.
Earlier forecast as the rising talent of UK boxing, he now is positioned trying to achieve expectations - maybe in what feels like a ultimate opportunity - under new promotional backing.
He started carefully, with the two boxers prepared to overcommit in a calculated initial rounds.
The challenger, whose only previous defeat came at super middleweight against his former opponent in two years ago after breaking his hand during the bout, was competing in only his second appearance at light heavyweight.
By the halfway stage, the underdog had stayed in contention, causing problems for Buatsi, who operated with a tight guard to narrowly win the cleaner periods.
The audience's tolerance wore thin amid frequent holding, with Parker falling to the floor various instances during grappling.
The underdog finished the stronger, but several stanzas were challenging to assess. Although, ex-champion the boxing analyst - commentating on the broadcast network - had it significantly in favor for the challenger, scoring for Buatsi just a single round.
Buatsi advances, but with the likes of power puncher Benavidez, and Russian champion Bivol ruling the division, the journey to titles - based on this performance - still appears challenging.
Ricky Hatton Tribute Motivates All-Manchester Fight
In the secondary fight, Arthur overcame Bradley Rea by close verdict in a excellent local rivalry contest to capture the European light-heavyweight belt.
The arena grew hushed for a profoundly moving homage prior to the bout as 10 bells sounded in memory of Manchester's own Ricky Hatton, who passed away 46 years old in September.
It was the initial significant broadcast match card in the urban center since Hatton's passing. As the concluding sound disappeared, the silence became a roar of "there's only one Ricky Hatton".
The fighting inside the ropes reflected the emotion. The eventual winner was floored by a left hook flush on the chin in the early round, standing uncertainly to his feet on the referee's count.
But the traditional red shorts of the fighter soon pressed ahead again. Across the ring, the opponent - in rival City blue - was injured early, significant bruising forming under his face as the pair traded powerful shots.
The challenger, twenty-seven, delivered effective strikes but Arthur, 34, matched the intensity with powerful upward punches as the pace hardly diminished over twelve rounds.
The victor narrowly won the decision with scoring tallies of even score, close margin and clearer margin, but both fighters were determined and courageous, everything their idol Hatton stood for.
