UK light-heavyweight Buatsi secured a victory yet underwhelming beginning to life under fresh promotional backing with a decision win over Zach Parker in Manchester.
The Olympic bronze medallist's punch output appeared to earn him a split decision in a close 10-round fight at the boxing arena.
But the challenger landed significant shots, delivering effective clean blows in a match where the styles didn't complement each other, with excessive holding spoiling the contest.
Two judges judged it 96-94 to Buatsi, with the third a 95-95.
"It wasn't my greatest display but what do champions do? They prevail," the victor said in the ringside as he was greeted with negative reactions from the crowd.
The British fighter returned to winning ways after his first professional defeat - an memorable fight with Callum Smith in February - to claim a twentieth professional win.
Several boxing experts thought Parker, thirty-one, merited the win but the British boxer suffered the second loss of his 28-match career.
Buatsi Secures Victory in Slow Match
The fighter's advancement has plateaued in recent times through promotional disputes and considerable time of lack of fights.
Previously predicted as the rising talent of UK boxing, he now is positioned trying to realize his potential - maybe in what seems like a last chance - under recent support.
He began cautiously, with neither fighter ready to be aggressive in a tentative opening few rounds.
Parker, whose sole prior loss came at super-middleweight against his former opponent in two years ago after damaging his hand in the contest, was competing in only his second bout at the higher weight class.
By the fight's midpoint, Parker had made it competitive, making life awkward for Buatsi, who operated with a tight guard to barely take the more effective stanzas.
The audience's tolerance decreased during frequent holding, with Parker going down several times during clinches.
Parker finished the stronger, but many rounds were hard to judge. Nevertheless, former world champion Carl Frampton - providing analysis for the broadcast network - had it strongly leaning for Parker, scoring for Buatsi just a single round.
Buatsi moves on, but with the presence of power puncher David Benavidez, and Eastern European fighter Dmitry Bivol dominating the weight class, the road to world glory - judging by this showing - still looks steep.
Hatton Memorial Inspires Manchester Derby Fight
In the secondary fight, Lyndon Arthur defeated Rea by divided decision in a terrific Manchester vs Manchester contest to win the continental belt.
The stadium fell silent for a profoundly moving tribute ahead of the contest as a bell ceremony rang in remembrance of local hero Ricky Hatton, who died 46 years old in last month.
It was the premier televised match card in the city since the passing of Hatton. As the concluding sound faded, the stillness became a chant of "there's only one Hatton".
The competition within the ring reflected the feeling. Arthur was floored by a powerful punch directly to the face in the initial stage, getting up unsteadily to his position on the eight count.
But the Manchester United-red attire of the fighter soon advanced again. On the opposite side, the opponent - in competitive blue - was marked up early, noticeable damage appearing under his orbital area as the fighters exchanged hard punches.
The challenger, 27, connected with strong blows but Arthur, thirty-four, matched the intensity with effective uppercuts as the intensity rarely dropped over the full distance.
The victor barely secured the decision with judges scorecards of even score, narrow lead and 115-112, but both fighters were relentless and full of heart, exactly what their idol the legend embodied.
