UK light heavyweight Buatsi secured a victory yet underwhelming debut to life under new promoters with a unanimous decision over Zach Parker in Manchester.
The Olympic bronze medallist's punch output appeared to earn him a majority decision in a competitive ten-round contest at the Co-op Live Arena.
But Parker found success, delivering effective single shots in a contest where the styles failed to mesh, with excessive holding marring the action.
Two judges scored it 96-94 in favor to the winner, with the third a 95-95 draw.
"It wasn't my greatest showing but how do champions respond? They prevail," Buatsi said in the ringside as he was greeted with disapproval from the crowd.
The British fighter returned to winning ways after his maiden career setback - an epic battle with his previous opponent in last winter - to secure a 20th career victory.
Several boxing experts thought the challenger, 31, merited the victory but the contender endured the second defeat of his 28-match professional journey.
Buatsi Earns Victory in Dull Encounter
Buatsi's progress has stalled in recent years through promotional disputes and extended periods of inactivity.
Earlier forecast as the next star of British boxing, he now finds himself trying to realize his potential - possibly in what feels like a final roll of the dice - under new promotional backing.
He began cautiously, with neither fighter willing to overcommit in a cagey early stages.
The challenger, whose single earlier setback came at super-middleweight against his former opponent in two years ago after suffering a hand injury in the contest, was participating in his second bout at the higher weight class.
By the halfway stage, the underdog had made it competitive, causing problems for the favorite, who operated with a tight guard to narrowly win the cleaner rounds.
The spectators' acceptance wore thin amid regular grabbing, with Parker slipping to the canvas several times during clinches.
The underdog ended stronger, but multiple periods were difficult to score. However, ex-champion Carl Frampton - working with Dazn - had it significantly in favor for the challenger, scoring for Buatsi just a single round.
The victor advances, but with the presence 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 Memorial Inspires Manchester Derby Contest
In the secondary fight, Arthur defeated Rea by divided decision in a excellent local rivalry fight to secure the European light heavyweight championship.
The stadium grew hushed for a profoundly moving memorial ahead of the contest as a bell ceremony tolled in memory of local hero Hatton, who passed away aged 46 in last month.
It was the first major televised boxing event in the location since Hatton's passing. As the concluding sound disappeared, the silence gave way to a roar of "there's only one Ricky Hatton".
The fighting within the ring matched the sentiment. Arthur was floored by a powerful punch directly to the face in the early round, getting up unsteadily to his position on the eight count.
But the red-colored attire of the fighter soon advanced again. From the other corner, Rea - in opposing blue - was damaged early, noticeable damage appearing under his face as the fighters traded hard punches.
The challenger, 27, connected with strong blows but Arthur, 34, fought fire with fire with stinging uppercuts as the intensity seldom decreased over twelve rounds.
The victor barely secured the verdict with official scores of 114-114, narrow lead and clearer margin, but both fighters were persistent and brave, exactly what their inspiration the legend embodied.
