UK light-heavyweight Buatsi secured a victory yet disappointing debut to life under fresh promotional backing with a unanimous decision over Zach Parker in the Manchester arena.
The Olympic bronze medallist's work rate appeared to earn him a majority decision in a close ten-round fight at the Manchester venue.
But Parker had his moments, connecting with powerful clean blows in a match where the styles failed to mesh, with excessive holding spoiling the action.
Two judges had it 96-94 for to the winner, with the third a 95-95 draw.
"It wasn't my greatest performance but what defines champions? They succeed," the victor stated in the ringside as he was greeted with boos from the crowd.
The Londoner returned to winning ways after his first professional defeat - an memorable fight with his previous opponent in last winter - to secure a 20th career victory.
Some ringside observers thought the challenger, 31, merited the decision but the British boxer endured the second setback of his 28-fight career.
Buatsi Secures Win in Uneventful Affair
Buatsi's progress has plateaued in the past few years through contract problems and long spells of inactivity.
Previously predicted as the rising talent of British boxing, he now stands trying to achieve expectations - possibly in what seems like a last chance - under new promotional backing.
He opened tentatively, with the two boxers willing to take risks in a tentative early stages.
The challenger, whose single earlier setback came at the lower weight class against his former opponent in 2022 after damaging his hand in the contest, was participating in his second bout at light heavyweight.
By the halfway stage, the underdog had kept it close, causing problems for the favorite, who utilized a solid defense to barely take the better rounds.
The audience's tolerance wore thin because of regular grabbing, with the challenger falling to the floor multiple occasions during close exchanges.
The underdog finished the stronger, but several stanzas were hard to judge. However, previous titleholder the boxing analyst - commentating on the broadcast network - had it strongly leaning for the challenger, scoring for Buatsi just a single round.
The victor progresses, but with the presence of heavy hitter Benavidez, and Eastern European fighter Dmitry Bivol dominating the weight class, the journey to titles - on this evidence - still looks steep.
Ricky Hatton Tribute Inspires Manchester Derby Contest
In the supporting bout, Arthur overcame Bradley Rea by split-decision in a excellent local rivalry contest to secure the European light heavyweight title.
The venue grew hushed for a extremely emotional memorial before the fight as 10 bells tolled in honor of local hero Ricky Hatton, who passed away at age 46 in September.
It was the first major televised boxing event in the location since Hatton's passing. As the last bell faded, the silence transitioned to a roar of "only one Ricky Hatton".
The fighting inside the ropes reflected the sentiment. The eventual winner was sent to the canvas by a significant blow directly to the chin in the early round, standing uncertainly to his footing on the eight count.
But the Manchester United-red attire of Arthur soon pressed ahead again. Across the ring, the opponent - in competitive blue - was damaged quickly, significant bruising developing under his eye as the fighters exchanged powerful shots.
The challenger, 27, connected with strong blows but Arthur, 34, fought fire with fire with effective uppercuts as the action rarely dropped over the full distance.
Arthur narrowly won the verdict with judges scorecards of even score, close margin and wider gap, but each competitor were persistent and brave, all the qualities their hero Hatton embodied.
