UK light heavyweight Buatsi earned a win yet underwhelming beginning to his career under recent management with a unanimous decision over Zach Parker in Manchester.
The Olympic medal winner's work rate appeared to earn him a split decision in a competitive ten-round bout at the Manchester venue.
But Parker found success, delivering effective clean blows in a fight where the techniques didn't complement each other, with frequent clinching spoiling the fight.
The scoring judges scored it 96-94 in favor to Buatsi, with the final judge a even score.
"It wasn't my greatest display but what defines champions? They win," Buatsi stated in the ring as he was greeted with negative reactions from the spectators.
The British fighter got back to winning after his first professional defeat - an memorable fight with Callum Smith in February - to secure a 20th career victory.
Several boxing experts believed the challenger, 31, deserved the decision but the Derbyshire fighter endured the second defeat of his 28-match professional journey.
Buatsi Claims Victory in Dull Affair
Buatsi's progress has plateaued in the past few years through contract problems and extended periods of lack of fights.
Earlier forecast as the next star of UK boxing, he now stands trying to fulfil that early promise - perhaps in what seems like a ultimate opportunity - under new promotional backing.
He opened tentatively, with the two boxers ready to overcommit in a calculated initial rounds.
Parker, whose single earlier setback came at the lower weight class against his former opponent in two years ago after suffering a hand injury during the bout, was competing in only his second appearance at the higher weight class.
By the halfway stage, Parker had made it competitive, making life awkward for Buatsi, who utilized a protective stance to barely take the more effective stanzas.
The audience's tolerance wore thin during regular grabbing, with the challenger slipping to the canvas multiple occasions during grappling.
Parker finished the stronger, but multiple periods were hard to judge. Nevertheless, former world champion the boxing analyst - providing analysis for the broadcast network - had it significantly in favor for the challenger, giving Buatsi just a single round.
Buatsi moves on, but with the presence of power puncher Benavidez, and Eastern European fighter Bivol ruling the division, the journey to titles - on this evidence - still appears challenging.
Hatton Tribute Fuels Manchester Derby Contest
In the co-main event, Lyndon Arthur defeated Rea by split-decision in a outstanding all-Manchester battle to secure the European light heavyweight title.
The arena became quiet for a deeply poignant homage prior to the bout as a bell ceremony rang in honor of local hero Hatton, who passed away 46 years old in September.
It was the initial significant broadcast fight night in the location since Hatton's death. As the last bell faded, the quiet gave way to a shout of "there's just one Ricky Hatton".
The action during the bout matched the emotion. Arthur was floored by a left hook directly to the face in the early round, getting up unsteadily to his footing on the eight count.
But the red-colored equipment of Arthur soon advanced again. From the other corner, Rea - in opposing blue - was injured soon, significant bruising developing under his orbital area as the fighters exchanged powerful shots.
The challenger, 27, landed power punches but the champion, thirty-four, fought fire with fire with powerful upward punches as the action rarely dropped over 12 rounds.
The victor narrowly won the decision with scoring tallies of even score, close margin and 115-112, but the two athletes were relentless and courageous, exactly what their idol Hatton embodied.
