British light-heavyweight Buatsi earned a win yet unimpressive start to his career under recent management with a points victory over Zach Parker in the Manchester arena.
The Olympic bronze medallist's punch output likely gained him a majority decision in a close ten-round fight at the boxing arena.
But Parker had his moments, delivering effective single shots in a fight where the approaches failed to mesh, with excessive holding spoiling the action.
Two judges had it 96-94 for to the winner, with the final judge a 95-95.
"It wasn't my best performance but how do champions respond? They win," Buatsi said in the ringside as he was met by disapproval from the crowd.
The Londoner bounced back after his initial pro loss - an memorable fight with his previous opponent in last winter - to secure a 20th career victory.
Several boxing experts believed Parker, 31, should have been awarded the decision but the British boxer endured the second defeat of his 28-fight professional journey.
Buatsi Earns Triumph in Dull Affair
The fighter's advancement has plateaued in recent years through contract problems and extended periods of inactivity.
Earlier forecast as the rising talent of British boxing, he now stands trying to achieve expectations - possibly in what feels like a ultimate opportunity - under new promotional backing.
He began cautiously, with both competitors willing to overcommit in a calculated opening few rounds.
The challenger, whose only previous defeat came at super middleweight against John Ryder in two years ago after damaging his hand during the bout, was competing in only his second bout at the higher weight class.
By the halfway stage, Parker had made it competitive, creating difficulties for Buatsi, who operated with a protective stance to narrowly win the better stanzas.
The spectators' acceptance diminished amid frequent holding, with Parker falling to the floor several times during grappling.
The underdog ended stronger, but many rounds were difficult to score. However, previous titleholder Carl Frampton - working with Dazn - had it particularly wide for the challenger, awarding Buatsi just only one stanza.
Buatsi progresses, but with the likes of heavy hitter Benavidez, and Russian star Bivol dominating the weight class, the road to world glory - judging by this showing - still looks steep.
Hatton Tribute Fuels Local Rivalry Battle
In the supporting bout, Arthur defeated Bradley Rea by split-decision in a terrific all-Manchester contest to capture the European light-heavyweight title.
The venue became quiet for a deeply poignant tribute before the fight as ten bells sounded in honor of Manchester's own Ricky Hatton, who succumbed aged 46 in recently.
It was the first major televised match card in the location since the passing of Hatton. As the last bell ended, the quiet gave way to a shout of "there's just one Hatton".
The competition during the bout equaled the sentiment. The eventual winner was sent to the canvas by a significant blow directly to the chin in the initial stage, standing uncertainly to his position on the count of eight.
But the Manchester United-red equipment of Arthur soon came forward again. Across the ring, the opponent - in opposing blue - was marked up early, noticeable damage forming under his face as the pair exchanged hard punches.
The challenger, 27, connected with strong blows but Arthur, thirty-four, fought fire with fire with stinging uppercuts as the pace seldom decreased over 12 rounds.
The victor edged the result with official scores of even score, close margin and wider gap, but the two athletes were persistent and brave, all the qualities their inspiration the legend embodied.
