UK light heavyweight Buatsi earned a win yet disappointing start to life under recent management with a unanimous decision over Zach Parker in Manchester.
The Olympic bronze medallist's work rate likely gained him a judges' verdict in a close 10-round contest at the boxing arena.
But Parker had his moments, connecting with powerful individual punches in a fight where the styles never quite clicked, with frequent clinching marring the action.
The scoring judges had it 96-94 to the winner, with the remaining official a even score.
"It wasn't my best display but how do champions respond? They win," Buatsi stated in the arena as he was met by disapproval from the audience.
The Londoner returned to winning ways after his initial pro loss - an thrilling contest with his previous opponent in February - to earn a 20th pro success.
Several boxing experts felt Parker, 31, merited the win but the contender endured the second defeat of his 28-match career.
Buatsi Secures Triumph in Uneventful Match
The fighter's advancement has stalled in recent years through promotional disputes and extended periods of inactivity.
Previously predicted as the rising talent of British boxing, he now finds himself trying to realize his potential - maybe in what feels like a final roll of the dice - under fresh management.
He began cautiously, with neither fighter prepared to take risks in a cagey initial rounds.
The challenger, whose sole prior loss 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 middle rounds, the underdog had kept it close, creating difficulties for Buatsi, who worked behind a protective stance to narrowly win the cleaner rounds.
The audience's tolerance decreased because of constant clinching, with Parker going down several times during grappling.
The underdog ended stronger, but several stanzas were challenging to assess. However, former world champion the boxing analyst - providing analysis for the broadcast network - had it significantly in favor for the challenger, awarding Buatsi just a single round.
Buatsi moves on, but with the caliber of hard hitter Benavidez, and Russian champion Bivol leading the category, the path to championship success - based on this performance - still looks steep.
Hatton Homage Inspires All-Manchester Contest
In the co-main event, Lyndon Arthur beat Rea by close verdict in a excellent local rivalry fight to win the European light heavyweight title.
The arena grew hushed for a deeply poignant tribute prior to the bout as a bell ceremony rang in memory of the city's native Hatton, who died aged 46 in recently.
It was the initial significant broadcast boxing event in the urban center since the passing of Hatton. As the last bell faded, the silence transitioned to a chant of "there's only one Ricky Hatton".
The competition within the ring reflected the feeling. Arthur was knocked down by a significant blow directly to the face in the second round, standing uncertainly to his position on the referee's count.
But the traditional red attire of the fighter soon advanced again. Across the ring, Rea - in opposing blue - was injured quickly, significant bruising forming under his face as the fighters landed powerful shots.
Rea, twenty-seven, connected with strong blows but Arthur, 34, matched the intensity with effective uppercuts as the action rarely dropped over twelve rounds.
Arthur narrowly won the result with judges scorecards of draw, 115-113 and 115-112, but the two athletes were relentless and courageous, all the qualities their inspiration Hatton stood for.
