UK light-heavyweight Buatsi made a winning yet underwhelming beginning to his career under recent management with a unanimous decision over Zach Parker in the Manchester arena.
The Olympic medal winner's punch output appeared to earn him a majority decision in a close 10-round bout at the Co-op Live Arena.
But Parker had his moments, landing some telling clean blows in a fight where the approaches failed to mesh, with frequent clinching marring the action.
The scoring judges scored it 96-94 to Buatsi, with the final judge a 95-95.
"It wasn't my greatest display but what defines champions? They prevail," the victor said in the ringside as he was greeted with disapproval from the crowd.
The Londoner bounced back after his initial pro loss - an epic battle with Callum Smith in last winter - to claim a 20th pro success.
Several boxing experts thought the challenger, 31, merited the victory but the Derbyshire fighter endured the second loss of his 28-match career.
Buatsi Claims Triumph in Dull Encounter
Buatsi's progress has plateaued in recent years through promotional disputes and long spells of inactivity.
Earlier forecast as the next star of the British fight scene, he now is positioned trying to realize his potential - possibly in what appears to be a last chance - under fresh management.
He began cautiously, with neither fighter ready to take risks in a calculated early stages.
Parker, whose only previous defeat 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 appearance at light-heavyweight.
By the halfway stage, the underdog had made it competitive, causing problems for the favorite, who utilized a solid defense to edge the better periods.
The audience's tolerance decreased during frequent holding, with the challenger going down several times during close exchanges.
The underdog ended stronger, but multiple periods were challenging to assess. Nevertheless, former world champion the boxing analyst - working with the broadcast network - had it significantly in favor for Parker, giving Buatsi just only one stanza.
Buatsi advances, but with the caliber of power puncher Benavidez, and Russian star Bivol dominating the weight class, the road to world glory - on this evidence - still looks steep.
Hatton Memorial Motivates All-Manchester Fight
In the co-main event, Lyndon Arthur beat Rea by divided decision in a outstanding Manchester vs Manchester fight to win the continental title.
The venue fell silent for a extremely emotional homage prior to the bout as ten bells sounded in memory of Manchester's own Hatton, who succumbed aged 46 in September.
It was the first major televised boxing event in the location since Hatton's death. As the concluding sound ended, the silence gave way to a chant of "there's only one Hatton".
The competition during the bout matched the sentiment. Arthur was knocked down by a significant blow directly to the jaw in the early round, rising shakily to his feet on the referee's count.
But the Manchester United-red shorts of the fighter soon came forward again. On the opposite side, the opponent - in opposing blue - was injured quickly, heavy swelling appearing under his orbital area as the fighters landed hard punches.
Rea, 27, delivered effective strikes but Arthur, thirty-four, fought fire with fire with stinging uppercuts as the pace seldom decreased over 12 rounds.
Arthur barely secured the result with judges scorecards of even score, 115-113 and clearer margin, but each competitor were determined and full of heart, everything their hero the legend represented.
