British light heavyweight Buatsi earned a win yet unimpressive debut to life under recent management with a decision win over Zach Parker in the Manchester arena.
The Olympic bronze medallist's work rate likely gained him a majority decision in a competitive 10-round contest at the Co-op Live Arena.
But the challenger had his moments, landing some telling single shots in a fight where the styles failed to mesh, with excessive holding disrupting the contest.
The scoring judges scored it 96-94 to Buatsi, with the final judge a 95-95.
"It wasn't my greatest showing but how do champions respond? They succeed," Buatsi stated in the ring as he was faced negative reactions from the audience.
The Londoner bounced back after his maiden career setback - an thrilling contest with Callum Smith in February - to claim a 20th career victory.
Several boxing experts felt the challenger, 31, deserved the decision but the Derbyshire fighter experienced the second setback of his 28-fight professional journey.
The Champion Earns Triumph in Uneventful Encounter
Buatsi's progress has stalled in the past few years through contract problems and considerable time of inactivity.
Previously predicted as the next star of UK boxing, he now is positioned trying to achieve expectations - possibly in what seems like a last chance - under fresh management.
He started carefully, with neither fighter ready to take risks in a tentative initial rounds.
Parker, whose only previous defeat came at super middleweight against John Ryder in two years ago after damaging his hand during the bout, was competing in only his second fight at light-heavyweight.
By the halfway stage, Parker had stayed in contention, creating difficulties for Buatsi, who worked behind a solid defense to barely take the better rounds.
The crowd's patience diminished amid constant clinching, with the challenger slipping to the canvas various instances during close exchanges.
The underdog ended stronger, but multiple periods were hard to judge. Nevertheless, former world champion the boxing analyst - commentating on Dazn - had it significantly in favor for the challenger, giving Buatsi just only one stanza.
The victor progresses, but with the likes of power puncher Benavidez, and Russian star Bivol dominating the weight class, the journey to titles - judging by this showing - still seems difficult.
Ricky Hatton Memorial Fuels Local Rivalry Fight
In the supporting bout, Lyndon Arthur beat Rea by divided decision in a terrific all-Manchester fight to win the continental title.
The venue fell silent for a deeply poignant tribute before the fight as ten bells tolled in memory of the city's native Hatton, who passed away at age 46 in September.
It was the first major televised fight night in the location since the passing of Hatton. As the last bell disappeared, the quiet gave way to a chant of "there's just one Ricky Hatton".
The fighting during the bout reflected the sentiment. Arthur was floored by a left hook squarely on the jaw in the second round, getting up unsteadily to his position on the eight count.
But the Manchester United-red attire of the fighter soon pressed ahead again. From the other corner, Rea - in opposing blue - was damaged quickly, significant bruising forming under his orbital area as the pair landed punishing blows.
Rea, twenty-seven, landed power punches but the champion, thirty-four, matched the intensity with effective uppercuts as the action hardly diminished over twelve rounds.
The victor edged the verdict with official scores of 114-114, narrow lead and wider gap, but both fighters were determined and courageous, exactly what their idol Hatton embodied.
