UK light heavyweight Buatsi made a winning yet unimpressive start to his career under recent management with a decision win over Zach Parker in Manchester.
The Olympic medal winner's work rate likely gained him a judges' verdict in a close 10-round fight at the Manchester venue.
But the challenger landed significant shots, connecting with powerful single shots in a fight where the styles failed to mesh, with frequent clinching spoiling the contest.
Two judges scored it 96-94 for to the winner, with the remaining official a even score.
"It wasn't my finest display but what defines champions? They win," Buatsi commented in the arena as he was faced boos from the crowd.
The British fighter bounced back after his initial pro loss - an memorable fight with his previous opponent in last winter - to earn a twentieth professional win.
Various analysts believed the challenger, thirty-one, deserved the victory but the British boxer endured the second loss of his 28-match professional journey.
Buatsi Earns Victory in Dull Match
The fighter's advancement has slowed in recent years through contract problems and long spells of inactivity.
Earlier forecast as the rising talent of UK boxing, he now is positioned trying to fulfil that early promise - possibly in what seems like a final roll of the dice - under recent support.
He began cautiously, with the two boxers prepared to overcommit in a calculated opening few rounds.
The challenger, whose sole prior loss came at super middleweight against John Ryder in two years ago after breaking his hand during the bout, was competing in only his second bout at light-heavyweight.
By the fight's midpoint, Parker had made it competitive, creating difficulties for the favorite, who worked behind a solid defense to barely take the better periods.
The audience's tolerance wore thin during regular grabbing, with Parker going down several times during grappling.
The underdog ended stronger, but multiple periods were hard to judge. Although, previous titleholder the boxing analyst - commentating on Dazn - had it strongly leaning for the challenger, scoring for Buatsi just one round.
Buatsi advances, but with the caliber of heavy hitter Benavidez, and Eastern European fighter Dmitry Bivol dominating the weight class, the road to world glory - judging by this showing - still seems difficult.
Hatton Homage Inspires All-Manchester Battle
In the secondary fight, Arthur beat Rea by divided decision in a excellent all-Manchester battle to secure the continental championship.
The arena grew hushed for a deeply poignant memorial prior to the bout as a bell ceremony rang in remembrance of Manchester's own Ricky Hatton, who succumbed aged 46 in recently.
It was the premier televised boxing event in the urban center since the passing of Hatton. As the last bell ended, the stillness gave way to a roar of "only one Ricky Hatton".
The action during the bout matched the emotion. The eventual winner was floored by a significant blow squarely on the chin in the second round, getting up unsteadily to his feet on the eight count.
But the Manchester United-red equipment of the fighter soon advanced again. From the other corner, the opponent - in competitive blue - was damaged soon, heavy swelling developing under his orbital area as the pair landed powerful shots.
Rea, 27, delivered effective strikes but Arthur, 34, responded in kind with stinging uppercuts as the intensity rarely dropped over 12 rounds.
Arthur barely secured the verdict with scoring tallies of 114-114, close margin and wider gap, but the two athletes were relentless and full of heart, all the qualities their inspiration the legend represented.
