UK light-heavyweight Buatsi earned a win yet disappointing debut to his career under new promoters with a decision win over Zach Parker in the Manchester arena.
The Olympic medal winner's work rate seemingly secured him a majority decision in a competitive ten-round contest at the boxing arena.
But Parker had his moments, connecting with powerful single shots in a contest where the techniques failed to mesh, with frequent clinching disrupting the contest.
Two judges had it 96-94 to the winner, with the remaining official a 95-95.
"It wasn't my best display but what defines champions? They win," Buatsi said in the arena as he was met by disapproval from the crowd.
The British fighter got back to winning after his initial pro loss - an memorable fight with his previous opponent in last winter - to earn a 20th career victory.
Some ringside observers believed Parker, thirty-one, should have been awarded the win but the Derbyshire fighter suffered the second setback of his 28-bout professional journey.
The Champion Claims Win in Uneventful Match
His career development has slowed in the past few years through contract problems and long spells of inactivity.
Previously predicted as the next star of British boxing, he now finds himself trying to realize his potential - possibly in what appears to be a final roll of the dice - under recent support.
He opened tentatively, with neither fighter prepared to be aggressive in a tentative initial rounds.
Parker, whose only previous defeat came at super-middleweight against his former opponent in two years ago after suffering a hand injury during the bout, was participating in his second fight at light-heavyweight.
By the middle rounds, Parker had stayed in contention, causing problems for Buatsi, who utilized a solid defense to edge the cleaner stanzas.
The crowd's patience wore thin amid regular grabbing, with the challenger slipping to the canvas multiple occasions during grappling.
Parker ended stronger, but many rounds were hard to judge. However, ex-champion Carl Frampton - providing analysis for Dazn - had it significantly in favor for the challenger, scoring for Buatsi just one round.
Buatsi advances, but with the presence of power puncher Benavidez, and Russian champion Bivol leading the category, the path to championship success - on this evidence - still looks steep.
Ricky Hatton Homage Inspires Manchester Derby Battle
In the secondary fight, Arthur defeated Bradley Rea by split-decision in a excellent all-Manchester contest to secure the European light-heavyweight belt.
The arena fell silent for a profoundly moving tribute ahead of the contest as 10 bells sounded in memory of local hero Hatton, who passed away aged 46 in last month.
It was the initial significant broadcast fight night in the city since the passing of Hatton. As the concluding sound ended, the quiet transitioned to a chant of "there's just one Hatton".
The competition inside the ropes equaled the feeling. The eventual winner was knocked down by a significant blow flush on the face in the initial stage, getting up unsteadily to his footing on the eight count.
But the traditional red shorts of Arthur soon advanced again. From the other corner, the opponent - in competitive blue - was injured soon, heavy swelling developing under his face as the duo exchanged powerful shots.
The challenger, twenty-seven, delivered effective strikes but the champion, 34, fought fire with fire with powerful upward punches as the intensity hardly diminished over twelve rounds.
The victor edged the result with official scores of 114-114, 115-113 and 115-112, but each competitor were persistent and full of heart, all the qualities their hero Hatton represented.
