British light heavyweight Buatsi secured a victory yet disappointing beginning to life under fresh promotional backing with a decision win over Zach Parker in Manchester.
The Olympic medal winner's punch output seemingly secured him a split decision in a tight 10-round bout at the Co-op Live Arena.
But Parker landed significant shots, landing some telling clean blows in a match where the techniques didn't complement each other, with constant grabbing spoiling the fight.
The scoring judges scored it 96-94 for to Buatsi, with the final judge a 95-95 draw.
"It wasn't my greatest display but what defines champions? They prevail," the victor said in the ring as he was faced boos from the crowd.
The Londoner got back to winning after his maiden career setback - an thrilling contest with Callum Smith in last winter - to claim a 20th pro success.
Some ringside observers thought Parker, 31, should have been awarded the win but the contender endured the second loss of his 28-fight professional journey.
Buatsi Earns Victory in Dull Match
Buatsi's progress has plateaued in the past few years through contract problems and extended periods of inactivity.
Previously predicted as the next star of British boxing, he now finds himself trying to achieve expectations - maybe in what feels like a last chance - under new promotional backing.
He began cautiously, with neither fighter ready to overcommit in a cagey early stages.
The challenger, whose single earlier setback came at super middleweight against John Ryder in two years ago after breaking his hand mid-fight, was competing in only his second bout at light-heavyweight.
By the middle rounds, the underdog had kept it close, causing problems for the favorite, who utilized a solid defense to narrowly win the more effective stanzas.
The spectators' acceptance diminished because of regular grabbing, with Parker going down various instances during close exchanges.
The underdog ended stronger, but several stanzas were difficult to score. However, former world champion Carl Frampton - providing analysis for the broadcast network - had it significantly in favor for the challenger, giving Buatsi just a single round.
The victor advances, but with the caliber of power puncher Benavidez, and Eastern European fighter Dmitry Bivol dominating the weight class, the road to world glory - on this evidence - still appears challenging.
Ricky Hatton Tribute Fuels Manchester Derby Contest
In the supporting bout, Arthur overcame Rea by split-decision in a terrific Manchester vs Manchester contest to secure the European light-heavyweight championship.
The venue fell silent for a deeply poignant homage before the fight as a bell ceremony rang in honor of Manchester's own Hatton, who died 46 years old in last month.
It was the premier televised fight night in the location since Hatton's death. As the concluding sound ended, the quiet transitioned to a shout of "there's just one Hatton".
The competition during the bout equaled the emotion. The eventual winner was knocked down by a powerful punch squarely on the face in the second round, standing uncertainly to his feet on the count of eight.
But the traditional red attire of the fighter soon came forward again. On the opposite side, the opponent - in opposing blue - was damaged soon, noticeable damage forming under his orbital area as the duo landed hard punches.
The challenger, 27, landed power punches but the champion, 34, fought fire with fire with effective uppercuts as the intensity seldom decreased over the full distance.
Arthur narrowly won the result with official scores of draw, narrow lead and wider gap, but each competitor were persistent and brave, all the qualities their inspiration the legend represented.
