UK light heavyweight Buatsi made a winning yet disappointing debut to his career under recent management with a points victory over Zach Parker in the Manchester arena.
The Olympic medal winner's work rate likely gained him a majority decision in a close 10-round bout at the boxing arena.
But Parker had his moments, connecting with powerful single shots in a match where the styles never quite clicked, with frequent clinching spoiling the action.
Two judges had it 96-94 to the winner, with the remaining official a even score.
"It wasn't my finest showing but what do champions do? They win," the victor commented in the ringside as he was greeted with boos from the crowd.
The Londoner bounced back after his first professional defeat - an thrilling contest with Callum Smith in February - to earn a twentieth professional win.
Various analysts felt the challenger, 31, merited the win but the Derbyshire fighter endured the second setback of his 28-bout professional journey.
Buatsi Claims Victory in Dull Encounter
Buatsi's progress has slowed in the past few years through contract problems and long spells of lack of fights.
Previously predicted as the future of UK boxing, he now is positioned trying to achieve expectations - perhaps in what seems like a ultimate opportunity - under fresh management.
He started carefully, with the two boxers ready to overcommit in a calculated early stages.
The challenger, whose sole prior loss came at the lower weight class against his former opponent in two years ago after breaking his hand mid-fight, was competing in only his second fight at light-heavyweight.
By the middle rounds, Parker had made it competitive, creating difficulties for the favorite, who worked behind a tight guard to narrowly win the cleaner periods.
The audience's tolerance decreased amid regular grabbing, with the challenger falling to the floor various instances during clinches.
The underdog closed well, but several stanzas were hard to judge. However, former world champion Carl Frampton - commentating on Dazn - had it particularly wide for Parker, giving Buatsi just one round.
The victor progresses, but with the presence of heavy hitter Benavidez, and Russian star Bivol ruling the division, the road to world glory - judging by this showing - still seems difficult.
Ricky Hatton Homage Motivates Manchester Derby Contest
In the secondary fight, Lyndon Arthur overcame Rea by divided decision in a terrific Manchester vs Manchester battle to win the European light-heavyweight belt.
The arena fell silent for a profoundly moving homage prior to the bout as 10 bells rang in remembrance of local hero Hatton, who died aged 46 in recently.
It was the initial significant broadcast match card in the urban center since Hatton's death. As the last bell disappeared, the quiet gave way to a roar of "only one Ricky Hatton".
The competition during the bout reflected the sentiment. The eventual winner was floored by a left hook directly to the jaw in the initial stage, getting up unsteadily to his footing on the referee's count.
But the traditional red attire of the fighter soon came forward again. From the other corner, Rea - in opposing blue - was damaged early, significant bruising developing under his face as the duo exchanged punishing blows.
Rea, twenty-seven, delivered effective strikes but the champion, thirty-four, matched the intensity with stinging uppercuts as the action rarely dropped over 12 rounds.
The victor edged the decision with judges scorecards of even score, narrow lead and wider gap, but both fighters were persistent and full of heart, all the qualities their hero Hatton represented.
