British light heavyweight Buatsi made a winning yet disappointing debut to his career under new promoters with a points victory over Zach Parker in Manchester.
The Olympic medal winner's work rate appeared to earn him a split decision in a tight ten-round fight at the boxing arena.
But the challenger had his moments, delivering effective single shots in a match where the styles failed to mesh, with constant grabbing spoiling the action.
The officials judged it 96-94 to Buatsi, with the remaining official a 95-95.
"It wasn't my greatest showing but what defines champions? They prevail," Buatsi said in the ring as he was met by disapproval from the spectators.
The Londoner returned to winning ways after his initial pro loss - an memorable fight with his previous opponent in February - to claim a 20th pro success.
Some ringside observers felt the challenger, 31, should have been awarded the victory but the British boxer endured the second setback of his 28-fight professional journey.
Buatsi Claims Triumph in Uneventful Match
His career development has plateaued in the past few years through management issues and considerable time of inactivity.
Once tipped as the future of British boxing, he now stands trying to realize his potential - maybe in what appears to be a ultimate opportunity - under fresh management.
He started carefully, with neither fighter prepared to take risks in a calculated early stages.
The challenger, whose single earlier setback came at super-middleweight against his former opponent in two years ago after breaking his hand in the contest, was participating in his second appearance at the higher weight class.
By the halfway stage, Parker had made it competitive, causing problems for the favorite, who operated with a protective stance to narrowly win the more effective stanzas.
The audience's tolerance wore thin during frequent holding, with the challenger slipping to the canvas several times during grappling.
Parker ended stronger, but multiple periods were challenging to assess. Although, former world champion the boxing analyst - commentating on Dazn - had it particularly wide for the challenger, scoring for Buatsi just a single round.
The victor moves on, but with the caliber of hard hitter Benavidez, and Russian champion Dmitry Bivol leading the category, the journey to titles - judging by this showing - still appears challenging.
Hatton Memorial Motivates All-Manchester Fight
In the co-main event, Arthur defeated Bradley Rea by close verdict in a excellent all-Manchester fight to win the European light heavyweight championship.
The venue became quiet for a deeply poignant memorial before the fight as a bell ceremony sounded in memory of local hero Ricky Hatton, who succumbed at age 46 in last month.
It was the first major televised fight night in the location since the passing of Hatton. As the last bell ended, the quiet gave way to a roar of "there's only one Ricky Hatton".
The fighting inside the ropes equaled the emotion. Arthur was knocked down by a significant blow squarely on the face in the second round, getting up unsteadily to his position on the eight count.
But the Manchester United-red equipment of Arthur soon pressed ahead again. On the opposite side, the opponent - in opposing blue - was marked up early, significant bruising forming under his face as the duo landed hard punches.
The challenger, twenty-seven, connected with strong blows but the champion, thirty-four, matched the intensity with effective uppercuts as the intensity seldom decreased over twelve rounds.
Arthur narrowly won the verdict with judges scorecards of 114-114, 115-113 and 115-112, but the two athletes were relentless and brave, exactly what their idol Hatton embodied.
