UK light-heavyweight Buatsi made a winning yet unimpressive beginning to life under new promoters with a points victory over Zach Parker in Manchester.
The Olympic bronze medallist's punch output appeared to earn him a split decision in a close ten-round fight at the boxing arena.
But the challenger found success, landing some telling single shots in a contest where the approaches didn't complement each other, with excessive holding marring the contest.
The officials scored it 96-94 in favor to the winner, with the remaining official a 95-95 draw.
"It wasn't my best performance but what do champions do? They prevail," the victor said in the arena as he was met by disapproval from the crowd.
The British fighter got back to winning after his maiden career setback - an thrilling contest with his previous opponent in February - to claim a twentieth professional win.
Some ringside observers believed the challenger, 31, deserved the decision but the contender experienced the second setback of his 28-fight professional journey.
The Champion Earns Triumph in Slow Match
Buatsi's progress has slowed in the past few years through contract problems and long spells of inactivity.
Earlier forecast as the future of UK boxing, he now is positioned trying to achieve expectations - possibly in what seems like a final roll of the dice - under new promotional backing.
He opened tentatively, with the two boxers prepared to overcommit in a calculated initial rounds.
The challenger, whose only previous defeat came at super-middleweight against John Ryder in two years ago after suffering a hand injury in the contest, was making just his second appearance at light heavyweight.
By the halfway stage, the underdog had stayed in contention, making life awkward for the favorite, who worked behind a tight guard to narrowly win the more effective rounds.
The audience's tolerance wore thin during regular grabbing, with Parker going down various instances during grappling.
The underdog ended stronger, but many rounds were difficult to score. However, previous titleholder the boxing analyst - providing analysis for Dazn - had it strongly leaning for the challenger, awarding Buatsi just a single round.
The victor advances, but with the likes of heavy hitter Benavidez, and Eastern European fighter Dmitry Bivol dominating the weight class, the road to world glory - on this evidence - still appears challenging.
Ricky Hatton Memorial Inspires Manchester Derby Battle
In the co-main event, Lyndon Arthur beat Rea by split-decision in a outstanding local rivalry contest to capture the European light heavyweight championship.
The stadium grew hushed for a extremely emotional homage ahead of the contest as a bell ceremony tolled in remembrance of the city's native Hatton, who died at age 46 in September.
It was the premier televised match card in the city since Hatton's passing. As the concluding sound ended, the silence became a chant of "there's only one Hatton".
The competition during the bout matched the sentiment. The eventual winner was knocked down by a significant blow squarely on the jaw in the second round, standing uncertainly to his footing on the referee's count.
But the red-colored attire of the fighter soon pressed ahead again. On the opposite side, Rea - in competitive blue - was damaged quickly, heavy swelling forming under his orbital area as the fighters exchanged powerful shots.
The challenger, 27, connected with strong blows but Arthur, 34, fought fire with fire with effective uppercuts as the intensity seldom decreased over twelve rounds.
The victor edged the decision with official scores of even score, 115-113 and clearer margin, but the two athletes were relentless and courageous, exactly what their hero the legend stood for.
